binutils-gdb/gdb/m68k-tdep.c

/* Target dependent code for the Motorola 68000 series.

   Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1999, 2000,
   2001, 2002, 2003, 2004 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 "dwarf2-frame.h"
#include "frame.h"
#include "frame-base.h"
#include "frame-unwind.h"
#include "symtab.h"
#include "gdbcore.h"
#include "value.h"
#include "gdb_string.h"
#include "gdb_assert.h"
#include "inferior.h"
#include "regcache.h"
#include "arch-utils.h"
#include "osabi.h"
#include "dis-asm.h"

#include "m68k-tdep.h"


#define P_LINKL_FP	0x480e
#define P_LINKW_FP	0x4e56
#define P_PEA_FP	0x4856
#define P_MOVEAL_SP_FP	0x2c4f
#define P_ADDAW_SP	0xdefc
#define P_ADDAL_SP	0xdffc
#define P_SUBQW_SP	0x514f
#define P_SUBQL_SP	0x518f
#define P_LEA_SP_SP	0x4fef
#define P_LEA_PC_A5	0x4bfb0170
#define P_FMOVEMX_SP	0xf227
#define P_MOVEL_SP	0x2f00
#define P_MOVEML_SP	0x48e7


#define REGISTER_BYTES_FP (16*4 + 8 + 8*12 + 3*4)
#define REGISTER_BYTES_NOFP (16*4 + 8)

/* Offset from SP to first arg on stack at first instruction of a function */
#define SP_ARG0 (1 * 4)

#if !defined (BPT_VECTOR)
#define BPT_VECTOR 0xf
#endif

#if !defined (REMOTE_BPT_VECTOR)
#define REMOTE_BPT_VECTOR 1
#endif


static const unsigned char *
m68k_local_breakpoint_from_pc (CORE_ADDR *pcptr, int *lenptr)
{
  static unsigned char break_insn[] = {0x4e, (0x40 | BPT_VECTOR)};
  *lenptr = sizeof (break_insn);
  return break_insn;
}


static int
m68k_register_bytes_ok (long numbytes)
{
  return ((numbytes == REGISTER_BYTES_FP)
	  || (numbytes == REGISTER_BYTES_NOFP));
}

/* Return the GDB type object for the "standard" data type of data in
   register N.  This should be int for D0-D7, SR, FPCONTROL and
   FPSTATUS, long double for FP0-FP7, and void pointer for all others
   (A0-A7, PC, FPIADDR).  Note, for registers which contain
   addresses return pointer to void, not pointer to char, because we
   don't want to attempt to print the string after printing the
   address.  */

static struct type *
m68k_register_type (struct gdbarch *gdbarch, int regnum)
{
  if (regnum >= FP0_REGNUM && regnum <= FP0_REGNUM + 7)
    return builtin_type_m68881_ext;

  if (regnum == M68K_FPI_REGNUM || regnum == PC_REGNUM)
    return builtin_type_void_func_ptr;

  if (regnum == M68K_FPC_REGNUM || regnum == M68K_FPS_REGNUM
      || regnum == PS_REGNUM)
    return builtin_type_int32;

  if (regnum >= M68K_A0_REGNUM && regnum <= M68K_A0_REGNUM + 7)
    return builtin_type_void_data_ptr;

  return builtin_type_int32;
}

/* Function: m68k_register_name
   Returns the name of the standard m68k register regnum. */

static const char *
m68k_register_name (int regnum)
{
  static char *register_names[] = {
    "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7",
    "a0", "a1", "a2", "a3", "a4", "a5", "fp", "sp",
    "ps", "pc",
    "fp0", "fp1", "fp2", "fp3", "fp4", "fp5", "fp6", "fp7",
    "fpcontrol", "fpstatus", "fpiaddr", "fpcode", "fpflags"
  };

  if (regnum < 0 ||
      regnum >= sizeof (register_names) / sizeof (register_names[0]))
    internal_error (__FILE__, __LINE__,
		    "m68k_register_name: illegal register number %d", regnum);
  else
    return register_names[regnum];
}

/* Extract from an array REGBUF containing the (raw) register state, a
   function return value of TYPE, and copy that, in virtual format,
   into VALBUF.  */

static void
m68k_extract_return_value (struct type *type, struct regcache *regcache,
			   void *valbuf)
{
  int len = TYPE_LENGTH (type);
  char buf[M68K_MAX_REGISTER_SIZE];

  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
      && TYPE_NFIELDS (type) == 1)
    {
      m68k_extract_return_value (TYPE_FIELD_TYPE (type, 0), regcache, valbuf);
      return;
    }

  if (len <= 4)
    {
      regcache_raw_read (regcache, M68K_D0_REGNUM, buf);
      memcpy (valbuf, buf + (4 - len), len);
    }
  else if (len <= 8)
    {
      regcache_raw_read (regcache, M68K_D0_REGNUM, buf);
      memcpy (valbuf, buf + (8 - len), len - 4);
      regcache_raw_read (regcache, M68K_D1_REGNUM,
			 (char *) valbuf + (len - 4));
    }
  else
    internal_error (__FILE__, __LINE__,
		    "Cannot extract return value of %d bytes long.", len);
}

/* Write into the appropriate registers a function return value stored
   in VALBUF of type TYPE, given in virtual format.  */

static void
m68k_store_return_value (struct type *type, struct regcache *regcache,
			 const void *valbuf)
{
  int len = TYPE_LENGTH (type);

  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
      && TYPE_NFIELDS (type) == 1)
    {
      m68k_store_return_value (TYPE_FIELD_TYPE (type, 0), regcache, valbuf);
      return;
    }

  if (len <= 4)
    regcache_raw_write_part (regcache, M68K_D0_REGNUM, 4 - len, len, valbuf);
  else if (len <= 8)
    {
      regcache_raw_write_part (regcache, M68K_D1_REGNUM, 8 - len,
			       len - 4, valbuf);
      regcache_raw_write (regcache, M68K_D0_REGNUM,
			  (char *) valbuf + (len - 4));
    }
  else
    internal_error (__FILE__, __LINE__,
		    "Cannot store return value of %d bytes long.", len);
}

/* Extract from REGCACHE, which contains the (raw) register state, the
   address in which a function should return its structure value, as a
   CORE_ADDR.  */

static CORE_ADDR
m68k_extract_struct_value_address (struct regcache *regcache)
{
  char buf[4];

  regcache_cooked_read (regcache, M68K_D0_REGNUM, buf);
  return extract_unsigned_integer (buf, 4);
}

static int
m68k_use_struct_convention (int gcc_p, struct type *type)
{
  enum struct_return struct_return;

  struct_return = gdbarch_tdep (current_gdbarch)->struct_return;
  return generic_use_struct_convention (struct_return == reg_struct_return,
					type);
}

/* A function that tells us whether the function invocation represented
   by fi does not have a frame on the stack associated with it.  If it
   does not, FRAMELESS is set to 1, else 0.  */

static int
m68k_frameless_function_invocation (struct frame_info *fi)
{
  if (get_frame_type (fi) == SIGTRAMP_FRAME)
    return 0;
  else
    return legacy_frameless_look_for_prologue (fi);
}

int
delta68_in_sigtramp (CORE_ADDR pc, char *name)
{
  if (name != NULL)
    return strcmp (name, "_sigcode") == 0;
  else
    return 0;
}

CORE_ADDR
delta68_frame_args_address (struct frame_info *frame_info)
{
  /* we assume here that the only frameless functions are the system calls
     or other functions who do not put anything on the stack. */
  if (get_frame_type (frame_info) == SIGTRAMP_FRAME)
    return get_frame_base (frame_info) + 12;
  else if (legacy_frameless_look_for_prologue (frame_info))
    {
      /* Check for an interrupted system call */
      if (get_next_frame (frame_info) && (get_frame_type (get_next_frame (frame_info)) == SIGTRAMP_FRAME))
	return get_frame_base (get_next_frame (frame_info)) + 16;
      else
	return get_frame_base (frame_info) + 4;
    }
  else
    return get_frame_base (frame_info);
}

CORE_ADDR
delta68_frame_saved_pc (struct frame_info *frame_info)
{
  return read_memory_unsigned_integer (delta68_frame_args_address (frame_info)
				       + 4, 4);
}

int
delta68_frame_num_args (struct frame_info *fi)
{
  int val;
  CORE_ADDR pc = DEPRECATED_FRAME_SAVED_PC (fi);
  int insn = read_memory_unsigned_integer (pc, 2);
  val = 0;
  if (insn == 0047757 || insn == 0157374)	/* lea W(sp),sp or addaw #W,sp */
    val = read_memory_integer (pc + 2, 2);
  else if ((insn & 0170777) == 0050217	/* addql #N, sp */
	   || (insn & 0170777) == 0050117)	/* addqw */
    {
      val = (insn >> 9) & 7;
      if (val == 0)
	val = 8;
    }
  else if (insn == 0157774)	/* addal #WW, sp */
    val = read_memory_integer (pc + 2, 4);
  val >>= 2;
  return val;
}

static CORE_ADDR
m68k_push_dummy_call (struct gdbarch *gdbarch, CORE_ADDR func_addr,
		      struct regcache *regcache, CORE_ADDR bp_addr, int nargs,
		      struct value **args, CORE_ADDR sp, int struct_return,
		      CORE_ADDR struct_addr)
{
  char buf[4];
  int i;

  /* Push arguments in reverse order.  */
  for (i = nargs - 1; i >= 0; i--)
    {
      struct type *value_type = VALUE_ENCLOSING_TYPE (args[i]);
      int len = TYPE_LENGTH (value_type);
      int container_len = (len + 3) & ~3;
      int offset;

      /* Non-scalars bigger than 4 bytes are left aligned, others are
	 right aligned.  */
      if ((TYPE_CODE (value_type) == TYPE_CODE_STRUCT
	   || TYPE_CODE (value_type) == TYPE_CODE_UNION
	   || TYPE_CODE (value_type) == TYPE_CODE_ARRAY)
	  && len > 4)
	offset = 0;
      else
	offset = container_len - len;
      sp -= container_len;
      write_memory (sp + offset, VALUE_CONTENTS_ALL (args[i]), len);
    }

  /* Store struct value address.  */
  if (struct_return)
    {
      store_unsigned_integer (buf, 4, struct_addr);
      regcache_cooked_write (regcache, M68K_A1_REGNUM, buf);
    }

  /* Store return address.  */
  sp -= 4;
  store_unsigned_integer (buf, 4, bp_addr);
  write_memory (sp, buf, 4);

  /* Finally, update the stack pointer...  */
  store_unsigned_integer (buf, 4, sp);
  regcache_cooked_write (regcache, M68K_SP_REGNUM, buf);

  /* ...and fake a frame pointer.  */
  regcache_cooked_write (regcache, M68K_FP_REGNUM, buf);

  /* DWARF2/GCC uses the stack address *before* the function call as a
     frame's CFA.  */
  return sp + 8;
}

struct m68k_frame_cache
{
  /* Base address.  */
  CORE_ADDR base;
  CORE_ADDR sp_offset;
  CORE_ADDR pc;

  /* Saved registers.  */
  CORE_ADDR saved_regs[M68K_NUM_REGS];
  CORE_ADDR saved_sp;

  /* Stack space reserved for local variables.  */
  long locals;
};

/* Allocate and initialize a frame cache.  */

static struct m68k_frame_cache *
m68k_alloc_frame_cache (void)
{
  struct m68k_frame_cache *cache;
  int i;

  cache = FRAME_OBSTACK_ZALLOC (struct m68k_frame_cache);

  /* Base address.  */
  cache->base = 0;
  cache->sp_offset = -4;
  cache->pc = 0;

  /* Saved registers.  We initialize these to -1 since zero is a valid
     offset (that's where %fp is supposed to be stored).  */
  for (i = 0; i < M68K_NUM_REGS; i++)
    cache->saved_regs[i] = -1;

  /* Frameless until proven otherwise.  */
  cache->locals = -1;

  return cache;
}

/* Check whether PC points at a code that sets up a new stack frame.
   If so, it updates CACHE and returns the address of the first
   instruction after the sequence that sets removes the "hidden"
   argument from the stack or CURRENT_PC, whichever is smaller.
   Otherwise, return PC.  */

static CORE_ADDR
m68k_analyze_frame_setup (CORE_ADDR pc, CORE_ADDR current_pc,
			  struct m68k_frame_cache *cache)
{
  int op;

  if (pc >= current_pc)
    return current_pc;

  op = read_memory_unsigned_integer (pc, 2);

  if (op == P_LINKW_FP || op == P_LINKL_FP || op == P_PEA_FP)
    {
      cache->saved_regs[M68K_FP_REGNUM] = 0;
      cache->sp_offset += 4;
      if (op == P_LINKW_FP)
	{
	  /* link.w %fp, #-N */
	  /* link.w %fp, #0; adda.l #-N, %sp */
	  cache->locals = -read_memory_integer (pc + 2, 2);

	  if (pc + 4 < current_pc && cache->locals == 0)
	    {
	      op = read_memory_unsigned_integer (pc + 4, 2);
	      if (op == P_ADDAL_SP)
		{
		  cache->locals = read_memory_integer (pc + 6, 4);
		  return pc + 10;
		}
	    }

	  return pc + 4;
	}
      else if (op == P_LINKL_FP)
	{
	  /* link.l %fp, #-N */
	  cache->locals = -read_memory_integer (pc + 2, 4);
	  return pc + 6;
	}
      else
	{
	  /* pea (%fp); movea.l %sp, %fp */
	  cache->locals = 0;

	  if (pc + 2 < current_pc)
	    {
	      op = read_memory_unsigned_integer (pc + 2, 2);

	      if (op == P_MOVEAL_SP_FP)
		{
		  /* move.l %sp, %fp */
		  return pc + 4;
		}
	    }

	  return pc + 2;
	}
    }
  else if ((op & 0170777) == P_SUBQW_SP || (op & 0170777) == P_SUBQL_SP)
    {
      /* subq.[wl] #N,%sp */
      /* subq.[wl] #8,%sp; subq.[wl] #N,%sp */
      cache->locals = (op & 07000) == 0 ? 8 : (op & 07000) >> 9;
      if (pc + 2 < current_pc)
	{
	  op = read_memory_unsigned_integer (pc + 2, 2);
	  if ((op & 0170777) == P_SUBQW_SP || (op & 0170777) == P_SUBQL_SP)
	    {
	      cache->locals += (op & 07000) == 0 ? 8 : (op & 07000) >> 9;
	      return pc + 4;
	    }
	}
      return pc + 2;
    }
  else if (op == P_ADDAW_SP || op == P_LEA_SP_SP)
    {
      /* adda.w #-N,%sp */
      /* lea (-N,%sp),%sp */
      cache->locals = -read_memory_integer (pc + 2, 2);
      return pc + 4;
    }
  else if (op == P_ADDAL_SP)
    {
      /* adda.l #-N,%sp */
      cache->locals = -read_memory_integer (pc + 2, 4);
      return pc + 6;
    }

  return pc;
}

/* Check whether PC points at code that saves registers on the stack.
   If so, it updates CACHE and returns the address of the first
   instruction after the register saves or CURRENT_PC, whichever is
   smaller.  Otherwise, return PC.  */

static CORE_ADDR
m68k_analyze_register_saves (CORE_ADDR pc, CORE_ADDR current_pc,
			     struct m68k_frame_cache *cache)
{
  if (cache->locals >= 0)
    {
      CORE_ADDR offset;
      int op;
      int i, mask, regno;

      offset = -4 - cache->locals;
      while (pc < current_pc)
	{
	  op = read_memory_unsigned_integer (pc, 2);
	  if (op == P_FMOVEMX_SP)
	    {
	      /* fmovem.x REGS,-(%sp) */
	      op = read_memory_unsigned_integer (pc + 2, 2);
	      if ((op & 0xff00) == 0xe000)
		{
		  mask = op & 0xff;
		  for (i = 0; i < 16; i++, mask >>= 1)
		    {
		      if (mask & 1)
			{
			  cache->saved_regs[i + M68K_FP0_REGNUM] = offset;
			  offset -= 12;
			}
		    }
		  pc += 4;
		}
	      else
		break;
	    }
	  else if ((op & 0170677) == P_MOVEL_SP)
	    {
	      /* move.l %R,-(%sp) */
	      regno = ((op & 07000) >> 9) | ((op & 0100) >> 3);
	      cache->saved_regs[regno] = offset;
	      offset -= 4;
	      pc += 2;
	    }
	  else if (op == P_MOVEML_SP)
	    {
	      /* movem.l REGS,-(%sp) */
	      mask = read_memory_unsigned_integer (pc + 2, 2);
	      for (i = 0; i < 16; i++, mask >>= 1)
		{
		  if (mask & 1)
		    {
		      cache->saved_regs[15 - i] = offset;
		      offset -= 4;
		    }
		}
	      pc += 4;
	    }
	  else
	    break;
	}
    }

  return pc;
}


/* Do a full analysis of the prologue at PC and update CACHE
   accordingly.  Bail out early if CURRENT_PC is reached.  Return the
   address where the analysis stopped.

   We handle all cases that can be generated by gcc.

   For allocating a stack frame:

   link.w %a6,#-N
   link.l %a6,#-N
   pea (%fp); move.l %sp,%fp
   link.w %a6,#0; add.l #-N,%sp
   subq.l #N,%sp
   subq.w #N,%sp
   subq.w #8,%sp; subq.w #N-8,%sp
   add.w #-N,%sp
   lea (-N,%sp),%sp
   add.l #-N,%sp

   For saving registers:

   fmovem.x REGS,-(%sp)
   move.l R1,-(%sp)
   move.l R1,-(%sp); move.l R2,-(%sp)
   movem.l REGS,-(%sp)

   For setting up the PIC register:

   lea (%pc,N),%a5

   */

static CORE_ADDR
m68k_analyze_prologue (CORE_ADDR pc, CORE_ADDR current_pc,
		       struct m68k_frame_cache *cache)
{
  unsigned int op;

  pc = m68k_analyze_frame_setup (pc, current_pc, cache);
  pc = m68k_analyze_register_saves (pc, current_pc, cache);
  if (pc >= current_pc)
    return current_pc;

  /* Check for GOT setup.  */
  op = read_memory_unsigned_integer (pc, 4);
  if (op == P_LEA_PC_A5)
    {
      /* lea (%pc,N),%a5 */
      return pc + 6;
    }

  return pc;
}

/* Return PC of first real instruction.  */

static CORE_ADDR
m68k_skip_prologue (CORE_ADDR start_pc)
{
  struct m68k_frame_cache cache;
  CORE_ADDR pc;
  int op;

  cache.locals = -1;
  pc = m68k_analyze_prologue (start_pc, (CORE_ADDR) -1, &cache);
  if (cache.locals < 0)
    return start_pc;
  return pc;
}

static CORE_ADDR
m68k_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  char buf[8];

  frame_unwind_register (next_frame, PC_REGNUM, buf);
  return extract_typed_address (buf, builtin_type_void_func_ptr);
}

/* Normal frames.  */

static struct m68k_frame_cache *
m68k_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  struct m68k_frame_cache *cache;
  char buf[4];
  int i;

  if (*this_cache)
    return *this_cache;

  cache = m68k_alloc_frame_cache ();
  *this_cache = cache;

  /* In principle, for normal frames, %fp holds the frame pointer,
     which holds the base address for the current stack frame.
     However, for functions that don't need it, the frame pointer is
     optional.  For these "frameless" functions the frame pointer is
     actually the frame pointer of the calling frame.  Signal
     trampolines are just a special case of a "frameless" function.
     They (usually) share their frame pointer with the frame that was
     in progress when the signal occurred.  */

  frame_unwind_register (next_frame, M68K_FP_REGNUM, buf);
  cache->base = extract_unsigned_integer (buf, 4);
  if (cache->base == 0)
    return cache;

  /* For normal frames, %pc is stored at 4(%fp).  */
  cache->saved_regs[M68K_PC_REGNUM] = 4;

  cache->pc = frame_func_unwind (next_frame);
  if (cache->pc != 0)
    m68k_analyze_prologue (cache->pc, frame_pc_unwind (next_frame), cache);

  if (cache->locals < 0)
    {
      /* We didn't find a valid frame, which means that CACHE->base
	 currently holds the frame pointer for our calling frame.  If
	 we're at the start of a function, or somewhere half-way its
	 prologue, the function's frame probably hasn't been fully
	 setup yet.  Try to reconstruct the base address for the stack
	 frame by looking at the stack pointer.  For truly "frameless"
	 functions this might work too.  */

      frame_unwind_register (next_frame, M68K_SP_REGNUM, buf);
      cache->base = extract_unsigned_integer (buf, 4) + cache->sp_offset;
    }

  /* Now that we have the base address for the stack frame we can
     calculate the value of %sp in the calling frame.  */
  cache->saved_sp = cache->base + 8;

  /* Adjust all the saved registers such that they contain addresses
     instead of offsets.  */
  for (i = 0; i < M68K_NUM_REGS; i++)
    if (cache->saved_regs[i] != -1)
      cache->saved_regs[i] += cache->base;

  return cache;
}

static void
m68k_frame_this_id (struct frame_info *next_frame, void **this_cache,
		    struct frame_id *this_id)
{
  struct m68k_frame_cache *cache = m68k_frame_cache (next_frame, this_cache);

  /* This marks the outermost frame.  */
  if (cache->base == 0)
    return;

  /* See the end of m68k_push_dummy_call.  */
  *this_id = frame_id_build (cache->base + 8, cache->pc);
}

static void
m68k_frame_prev_register (struct frame_info *next_frame, void **this_cache,
			  int regnum, int *optimizedp,
			  enum lval_type *lvalp, CORE_ADDR *addrp,
			  int *realnump, void *valuep)
{
  struct m68k_frame_cache *cache = m68k_frame_cache (next_frame, this_cache);

  gdb_assert (regnum >= 0);

  if (regnum == M68K_SP_REGNUM && cache->saved_sp)
    {
      *optimizedp = 0;
      *lvalp = not_lval;
      *addrp = 0;
      *realnump = -1;
      if (valuep)
	{
	  /* Store the value.  */
	  store_unsigned_integer (valuep, 4, cache->saved_sp);
	}
      return;
    }

  if (regnum < M68K_NUM_REGS && cache->saved_regs[regnum] != -1)
    {
      *optimizedp = 0;
      *lvalp = lval_memory;
      *addrp = cache->saved_regs[regnum];
      *realnump = -1;
      if (valuep)
	{
	  /* Read the value in from memory.  */
	  read_memory (*addrp, valuep,
		       register_size (current_gdbarch, regnum));
	}
      return;
    }

  frame_register_unwind (next_frame, regnum,
			 optimizedp, lvalp, addrp, realnump, valuep);
}

static const struct frame_unwind m68k_frame_unwind =
{
  NORMAL_FRAME,
  m68k_frame_this_id,
  m68k_frame_prev_register
};

static const struct frame_unwind *
m68k_frame_sniffer (struct frame_info *next_frame)
{
  return &m68k_frame_unwind;
}

/* Signal trampolines.  */

static struct m68k_frame_cache *
m68k_sigtramp_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  struct m68k_frame_cache *cache;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
  struct m68k_sigtramp_info info;
  char buf[4];
  int i;

  if (*this_cache)
    return *this_cache;

  cache = m68k_alloc_frame_cache ();

  frame_unwind_register (next_frame, M68K_SP_REGNUM, buf);
  cache->base = extract_unsigned_integer (buf, 4) - 4;

  info = tdep->get_sigtramp_info (next_frame);

  for (i = 0; i < M68K_NUM_REGS; i++)
    if (info.sc_reg_offset[i] != -1)
      cache->saved_regs[i] = info.sigcontext_addr + info.sc_reg_offset[i];

  *this_cache = cache;
  return cache;
}

static void
m68k_sigtramp_frame_this_id (struct frame_info *next_frame, void **this_cache,
			     struct frame_id *this_id)
{
  struct m68k_frame_cache *cache =
    m68k_sigtramp_frame_cache (next_frame, this_cache);

  /* See the end of m68k_push_dummy_call.  */
  *this_id = frame_id_build (cache->base + 8, frame_pc_unwind (next_frame));
}

static void
m68k_sigtramp_frame_prev_register (struct frame_info *next_frame,
				   void **this_cache,
				   int regnum, int *optimizedp,
				   enum lval_type *lvalp, CORE_ADDR *addrp,
				   int *realnump, void *valuep)
{
  /* Make sure we've initialized the cache.  */
  m68k_sigtramp_frame_cache (next_frame, this_cache);

  m68k_frame_prev_register (next_frame, this_cache, regnum,
			    optimizedp, lvalp, addrp, realnump, valuep);
}

static const struct frame_unwind m68k_sigtramp_frame_unwind =
{
  SIGTRAMP_FRAME,
  m68k_sigtramp_frame_this_id,
  m68k_sigtramp_frame_prev_register
};

static const struct frame_unwind *
m68k_sigtramp_frame_sniffer (struct frame_info *next_frame)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  char *name;

  /* We shouldn't even bother to try if the OSABI didn't register
     a get_sigtramp_info handler.  */
  if (!gdbarch_tdep (current_gdbarch)->get_sigtramp_info)
    return NULL;

  find_pc_partial_function (pc, &name, NULL, NULL);
  if (PC_IN_SIGTRAMP (pc, name))
    return &m68k_sigtramp_frame_unwind;

  return NULL;
}

static CORE_ADDR
m68k_frame_base_address (struct frame_info *next_frame, void **this_cache)
{
  struct m68k_frame_cache *cache = m68k_frame_cache (next_frame, this_cache);

  return cache->base;
}

static const struct frame_base m68k_frame_base =
{
  &m68k_frame_unwind,
  m68k_frame_base_address,
  m68k_frame_base_address,
  m68k_frame_base_address
};

static struct frame_id
m68k_unwind_dummy_id (struct gdbarch *gdbarch, struct frame_info *next_frame)
{
  char buf[4];
  CORE_ADDR fp;

  frame_unwind_register (next_frame, M68K_FP_REGNUM, buf);
  fp = extract_unsigned_integer (buf, 4);

  /* See the end of m68k_push_dummy_call.  */
  return frame_id_build (fp + 8, frame_pc_unwind (next_frame));
}

#ifdef USE_PROC_FS		/* Target dependent support for /proc */

#include <sys/procfs.h>

/* Prototypes for supply_gregset etc. */
#include "gregset.h"

/*  The /proc interface divides the target machine's register set up into
   two different sets, the general register set (gregset) and the floating
   point register set (fpregset).  For each set, there is an ioctl to get
   the current register set and another ioctl to set the current values.

   The actual structure passed through the ioctl interface is, of course,
   naturally machine dependent, and is different for each set of registers.
   For the m68k for example, the general register set is typically defined
   by:

   typedef int gregset_t[18];

   #define      R_D0    0
   ...
   #define      R_PS    17

   and the floating point set by:

   typedef      struct fpregset {
   int  f_pcr;
   int  f_psr;
   int  f_fpiaddr;
   int  f_fpregs[8][3];         (8 regs, 96 bits each)
   } fpregset_t;

   These routines provide the packing and unpacking of gregset_t and
   fpregset_t formatted data.

 */

/* Atari SVR4 has R_SR but not R_PS */

#if !defined (R_PS) && defined (R_SR)
#define R_PS R_SR
#endif

/*  Given a pointer to a general register set in /proc format (gregset_t *),
   unpack the register contents and supply them as gdb's idea of the current
   register values. */

void
supply_gregset (gregset_t *gregsetp)
{
  int regi;
  greg_t *regp = (greg_t *) gregsetp;

  for (regi = 0; regi < R_PC; regi++)
    {
      supply_register (regi, (char *) (regp + regi));
    }
  supply_register (PS_REGNUM, (char *) (regp + R_PS));
  supply_register (PC_REGNUM, (char *) (regp + R_PC));
}

void
fill_gregset (gregset_t *gregsetp, int regno)
{
  int regi;
  greg_t *regp = (greg_t *) gregsetp;

  for (regi = 0; regi < R_PC; regi++)
    {
      if (regno == -1 || regno == regi)
	regcache_collect (regi, regp + regi);
    }
  if (regno == -1 || regno == PS_REGNUM)
    regcache_collect (PS_REGNUM, regp + R_PS);
  if (regno == -1 || regno == PC_REGNUM)
    regcache_collect (PC_REGNUM, regp + R_PC);
}

#if defined (FP0_REGNUM)

/*  Given a pointer to a floating point register set in /proc format
   (fpregset_t *), unpack the register contents and supply them as gdb's
   idea of the current floating point register values. */

void
supply_fpregset (fpregset_t *fpregsetp)
{
  int regi;
  char *from;

  for (regi = FP0_REGNUM; regi < M68K_FPC_REGNUM; regi++)
    {
      from = (char *) &(fpregsetp->f_fpregs[regi - FP0_REGNUM][0]);
      supply_register (regi, from);
    }
  supply_register (M68K_FPC_REGNUM, (char *) &(fpregsetp->f_pcr));
  supply_register (M68K_FPS_REGNUM, (char *) &(fpregsetp->f_psr));
  supply_register (M68K_FPI_REGNUM, (char *) &(fpregsetp->f_fpiaddr));
}

/*  Given a pointer to a floating point register set in /proc format
   (fpregset_t *), update the register specified by REGNO from gdb's idea
   of the current floating point register set.  If REGNO is -1, update
   them all. */

void
fill_fpregset (fpregset_t *fpregsetp, int regno)
{
  int regi;

  for (regi = FP0_REGNUM; regi < M68K_FPC_REGNUM; regi++)
    {
      if (regno == -1 || regno == regi)
	regcache_collect (regi, &fpregsetp->f_fpregs[regi - FP0_REGNUM][0]);
    }
  if (regno == -1 || regno == M68K_FPC_REGNUM)
    regcache_collect (M68K_FPC_REGNUM, &fpregsetp->f_pcr);
  if (regno == -1 || regno == M68K_FPS_REGNUM)
    regcache_collect (M68K_FPS_REGNUM, &fpregsetp->f_psr);
  if (regno == -1 || regno == M68K_FPI_REGNUM)
    regcache_collect (M68K_FPI_REGNUM, &fpregsetp->f_fpiaddr);
}

#endif /* defined (FP0_REGNUM) */

#endif /* USE_PROC_FS */

/* Figure out where the longjmp will land.  Slurp the args out of the stack.
   We expect the first arg to be a pointer to the jmp_buf structure from which
   we extract the pc (JB_PC) that we will land at.  The pc is copied into PC.
   This routine returns true on success. */

int
m68k_get_longjmp_target (CORE_ADDR *pc)
{
  char *buf;
  CORE_ADDR sp, jb_addr;
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (tdep->jb_pc < 0)
    {
      internal_error (__FILE__, __LINE__,
		      "m68k_get_longjmp_target: not implemented");
      return 0;
    }

  buf = alloca (TARGET_PTR_BIT / TARGET_CHAR_BIT);
  sp = read_register (SP_REGNUM);

  if (target_read_memory (sp + SP_ARG0,	/* Offset of first arg on stack */
			  buf, TARGET_PTR_BIT / TARGET_CHAR_BIT))
    return 0;

  jb_addr = extract_unsigned_integer (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);

  if (target_read_memory (jb_addr + tdep->jb_pc * tdep->jb_elt_size, buf,
			  TARGET_PTR_BIT / TARGET_CHAR_BIT))
    return 0;

  *pc = extract_unsigned_integer (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);
  return 1;
}

/* Function: m68k_gdbarch_init
   Initializer function for the m68k gdbarch vector.
   Called by gdbarch.  Sets up the gdbarch vector(s) for this target. */

static struct gdbarch *
m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
  struct gdbarch_tdep *tdep = NULL;
  struct gdbarch *gdbarch;

  /* find a candidate among the list of pre-declared architectures. */
  arches = gdbarch_list_lookup_by_info (arches, &info);
  if (arches != NULL)
    return (arches->gdbarch);

  tdep = xmalloc (sizeof (struct gdbarch_tdep));
  gdbarch = gdbarch_alloc (&info, tdep);

  set_gdbarch_long_double_format (gdbarch, &floatformat_m68881_ext);
  set_gdbarch_long_double_bit (gdbarch, 96);

  set_gdbarch_skip_prologue (gdbarch, m68k_skip_prologue);
  set_gdbarch_breakpoint_from_pc (gdbarch, m68k_local_breakpoint_from_pc);

  /* Stack grows down. */
  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
  set_gdbarch_parm_boundary (gdbarch, 32);

  set_gdbarch_believe_pcc_promotion (gdbarch, 1);
  set_gdbarch_decr_pc_after_break (gdbarch, 2);

  set_gdbarch_extract_return_value (gdbarch, m68k_extract_return_value);
  set_gdbarch_store_return_value (gdbarch, m68k_store_return_value);
  set_gdbarch_deprecated_extract_struct_value_address (gdbarch, m68k_extract_struct_value_address);
  set_gdbarch_use_struct_convention (gdbarch, m68k_use_struct_convention);

  set_gdbarch_deprecated_frameless_function_invocation (gdbarch, m68k_frameless_function_invocation);
  set_gdbarch_frame_args_skip (gdbarch, 8);

  set_gdbarch_register_type (gdbarch, m68k_register_type);
  set_gdbarch_register_name (gdbarch, m68k_register_name);
  set_gdbarch_num_regs (gdbarch, 29);
  set_gdbarch_register_bytes_ok (gdbarch, m68k_register_bytes_ok);
  set_gdbarch_sp_regnum (gdbarch, M68K_SP_REGNUM);
  set_gdbarch_pc_regnum (gdbarch, M68K_PC_REGNUM);
  set_gdbarch_ps_regnum (gdbarch, M68K_PS_REGNUM);
  set_gdbarch_fp0_regnum (gdbarch, M68K_FP0_REGNUM);

  set_gdbarch_push_dummy_call (gdbarch, m68k_push_dummy_call);

  /* Disassembler.  */
  set_gdbarch_print_insn (gdbarch, print_insn_m68k);

#if defined JB_PC && defined JB_ELEMENT_SIZE
  tdep->jb_pc = JB_PC;
  tdep->jb_elt_size = JB_ELEMENT_SIZE;
#else
  tdep->jb_pc = -1;
#endif
  tdep->get_sigtramp_info = NULL;
  tdep->struct_return = pcc_struct_return;

  /* Frame unwinder.  */
  set_gdbarch_unwind_dummy_id (gdbarch, m68k_unwind_dummy_id);
  set_gdbarch_unwind_pc (gdbarch, m68k_unwind_pc);

  /* Hook in the DWARF CFI frame unwinder.  */
  frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);

  frame_base_set_default (gdbarch, &m68k_frame_base);

  /* Hook in ABI-specific overrides, if they have been registered.  */
  gdbarch_init_osabi (info, gdbarch);

  /* Now we have tuned the configuration, set a few final things,
     based on what the OS ABI has told us.  */

  if (tdep->jb_pc >= 0)
    set_gdbarch_get_longjmp_target (gdbarch, m68k_get_longjmp_target);

  frame_unwind_append_sniffer (gdbarch, m68k_sigtramp_frame_sniffer);
  frame_unwind_append_sniffer (gdbarch, m68k_frame_sniffer);

  return gdbarch;
}


static void
m68k_dump_tdep (struct gdbarch *current_gdbarch, struct ui_file *file)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (tdep == NULL)
    return;
}

extern initialize_file_ftype _initialize_m68k_tdep; /* -Wmissing-prototypes */

void
_initialize_m68k_tdep (void)
{
  gdbarch_register (bfd_arch_m68k, m68k_gdbarch_init, m68k_dump_tdep);
}