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/* Target-dependent code for GNU/Linux on Alpha.

   Copyright 2002 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 2 of the License, or

   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

#include "defs.h"

#include "frame.h"

#include "gdbcore.h"

#include "value.h"

#include "alpha-tdep.h"

/* Under GNU/Linux, signal handler invocations can be identified by the

   designated code sequence that is used to return from a signal

   handler.  In particular, the return address of a signal handler

   points to the following sequence (the first instruction is quadword

   aligned):

   bis $30,$30,$16

   addq $31,0x67,$0

   call_pal callsys

   Each instruction has a unique encoding, so we simply attempt to

   match the instruction the pc is pointing to with any of the above

   instructions.  If there is a hit, we know the offset to the start

   of the designated sequence and can then check whether we really are

   executing in a designated sequence.  If not, -1 is returned,

   otherwise the offset from the start of the desingated sequence is

   returned.

   There is a slight chance of false hits: code could jump into the

   middle of the designated sequence, in which case there is no

   guarantee that we are in the middle of a sigreturn syscall.  Don't

   think this will be a problem in praxis, though.  */

LONGEST

alpha_linux_sigtramp_offset (CORE_ADDR pc)

{

  unsigned int i[3], w;

  long off;

  if (read_memory_nobpt (pc, (char *) &w, 4) != 0)

    return -1;

  off = -1;

  switch (w)

    {

    case 0x47de0410:

      off = 0;

      break;                    /* bis $30,$30,$16 */

    case 0x43ecf400:

      off = 4;

      break;                    /* addq $31,0x67,$0 */

    case 0x00000083:

      off = 8;

      break;                    /* call_pal callsys */

    default:

      return -1;

    }

  pc -= off;

  if (pc & 0x7)

    {

      /* designated sequence is not quadword aligned */

      return -1;

    }

  if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0)

    return -1;

  if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083)

    return off;

  return -1;

}

static int

alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)

{

  return (alpha_linux_sigtramp_offset (pc) >= 0);

}

static CORE_ADDR

alpha_linux_sigcontext_addr (struct frame_info *frame)

{

  return (frame->frame - 0x298); /* sizeof(struct sigcontext) */

}

static void

alpha_linux_init_abi (struct gdbarch_info info,

                      struct gdbarch *gdbarch)

{

  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);

  tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;

  tdep->sigcontext_addr = alpha_linux_sigcontext_addr;

  tdep->jb_pc = 2;

  tdep->jb_elt_size = 8;

}

void

_initialize_alpha_linux_tdep (void)

{

  gdbarch_register_osabi (bfd_arch_alpha, GDB_OSABI_LINUX,

                          alpha_linux_init_abi);

}