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

/* Definitions for thread-local data handling.  Hurd/i386 version.
   Copyright (C) 2003-2020 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, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _I386_TLS_H
#define _I386_TLS_H


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


#ifndef __ASSEMBLER__
# include <dl-dtv.h>

/* Type of the TCB.  */
typedef struct
{
  void *tcb;			/* Points to this structure.  */
  dtv_t *dtv;			/* Vector of pointers to TLS data.  */
  thread_t self;		/* This thread's control port.  */
  int multiple_threads;
  uintptr_t sysinfo;
  uintptr_t stack_guard;
  uintptr_t pointer_guard;
  int gscope_flag;
  int private_futex;
  /* Reservation of some values for the TM ABI.  */
  void *__private_tm[4];
  /* GCC split stack support.  */
  void *__private_ss;

  /* Keep these fields last, so offsets of fields above can continue being
     compatible with the i386 Linux version.  */
  mach_port_t reply_port;      /* This thread's reply port.  */
  struct hurd_sigstate *_hurd_sigstate;
} tcbhead_t;
#endif

/* Return tcbhead_t from a TLS segment descriptor.  */
# define HURD_DESC_TLS(desc)						      \
  ({									      \
   (tcbhead_t *) (   (desc->low_word >> 16)				      \
                  | ((desc->high_word & 0xff) << 16)			      \
                  |  (desc->high_word & 0xff000000));			      \
  })

/* Return 1 if TLS is not initialized yet.  */
#define __LIBC_NO_TLS()							      \
  ({ unsigned short ds, gs;						      \
     asm ("movw %%ds,%w0; movw %%gs,%w1" : "=q" (ds), "=q" (gs));	      \
     __builtin_expect (ds == gs, 0); })

/* 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
#define TLS_DTV_AT_TP	0

/* Alignment requirement for TCB.

   Some processors such as Intel Atom pay a big penalty on every
   access using a segment override if that segment's base is not
   aligned to the size of a cache line.  (See Intel 64 and IA-32
   Architectures Optimization Reference Manual, section 13.3.3.3,
   "Segment Base".)  On such machines, a cache line is 64 bytes.  */
#define TCB_ALIGNMENT		64

#ifndef __ASSEMBLER__

/* 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) ((void) (thr), (void) (sel), (void) (desc), MIG_BAD_ID)
# endif

# include <errno.h>
# include <assert.h>

# define HURD_TLS_DESC_DECL(desc, tcb)					      \
  struct descriptor desc =						      \
    {				/* low word: */				      \
      0xffff			/* limit 0..15 */			      \
      | (((unsigned int) (tcb)) << 16) /* base 0..15 */			      \
      ,				/* high word: */			      \
      ((((unsigned int) (tcb)) >> 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 */		      \
      | (((unsigned int) (tcb)) & 0xff000000) /* base 24..31 */		      \
    }

# define HURD_SEL_LDT(sel) (__builtin_expect ((sel) & 4, 0))

static inline const char * __attribute__ ((unused))
_hurd_tls_init (tcbhead_t *tcb)
{
  HURD_TLS_DESC_DECL (desc, tcb);
  thread_t self = __mach_thread_self ();
  const char *msg = NULL;

  /* This field is used by TLS accesses to get our "thread pointer"
     from the TLS point of view.  */
  tcb->tcb = tcb;
  /* We always at least start the sigthread anyway.  */
  tcb->multiple_threads = 1;

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

  /* Now install the new selector.  */
  asm volatile ("mov %w0, %%gs" :: "q" (sel));

out:
  __mach_port_deallocate (__mach_task_self (), self);
  return msg;
}

/* 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) \
    _hurd_tls_init ((tcbhead_t *) (descr))

/* Return the TCB address of the current thread.  */
# define THREAD_SELF							      \
  ({ tcbhead_t *__tcb;							      \
     __asm__ ("movl %%gs:%c1,%0" : "=r" (__tcb)				      \
	      : "i" (offsetof (tcbhead_t, tcb)));			      \
     __tcb;})

/* Return the TCB address of a thread given its state.
   Note: this is expensive.  */
# define THREAD_TCB(thread, thread_state)				      \
  ({ int __sel = (thread_state)->basic.gs;				      \
     struct descriptor __desc, *___desc = &__desc;			      \
     unsigned int __count = 1;						      \
     kern_return_t __err;						      \
     if (HURD_SEL_LDT (__sel))						      \
       __err = __i386_get_ldt ((thread), __sel, 1, &___desc, &__count);	      \
     else								      \
       __err = __i386_get_gdt ((thread), __sel, &__desc);		      \
     assert_perror (__err);						      \
     assert (__count == 1);						      \
     HURD_DESC_TLS (___desc);})

/* Install new dtv for current thread.  */
# define INSTALL_NEW_DTV(dtvp)						      \
  ({ asm volatile ("movl %0,%%gs:%P1"					      \
		   : : "ir" (dtvp), "i" (offsetof (tcbhead_t, dtv))); })

/* Return the address of the dtv for the current thread.  */
# define THREAD_DTV()							      \
  ({ dtv_t *_dtv;							      \
     asm ("movl %%gs:%P1,%0" : "=q" (_dtv) : "i" (offsetof (tcbhead_t, dtv)));\
     _dtv; })

# include <mach/machine/thread_status.h>

/* Set up TLS in the new thread of a fork child, copying from the original.  */
static inline kern_return_t __attribute__ ((unused))
_hurd_tls_fork (thread_t child, thread_t orig, struct i386_thread_state *state)
{
  /* Fetch the selector set by _hurd_tls_init.  */
  int sel;
  asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
  if (sel == state->ds)		/* _hurd_tls_init was never called.  */
    return 0;

  struct descriptor desc, *_desc = &desc;
  error_t err;
  unsigned int count = 1;

  if (HURD_SEL_LDT (sel))
    err = __i386_get_ldt (orig, sel, 1, &_desc, &count);
  else
    err = __i386_get_gdt (orig, sel, &desc);

  assert_perror (err);
  if (err)
    return err;

  if (HURD_SEL_LDT (sel))
    err = __i386_set_ldt (child, sel, &desc, 1);
  else
    err = __i386_set_gdt (child, &sel, desc);

  state->gs = sel;
  return err;
}

static inline kern_return_t __attribute__ ((unused))
_hurd_tls_new (thread_t child, struct i386_thread_state *state, tcbhead_t *tcb)
{
  /* Fetch the selector set by _hurd_tls_init.  */
  int sel;
  asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
  if (sel == state->ds)		/* _hurd_tls_init was never called.  */
    return 0;

  HURD_TLS_DESC_DECL (desc, tcb);
  error_t err;

  tcb->tcb = tcb;
  tcb->self = child;

  if (HURD_SEL_LDT (sel))
    err = __i386_set_ldt (child, sel, &desc, 1);
  else
    err = __i386_set_gdt (child, &sel, desc);

  state->gs = sel;
  return err;
}

#endif	/* !__ASSEMBLER__ */

#endif	/* i386/tls.h */