binutils-gdb/gdb/mem-break.c

/* Simulate breakpoints by patching locations in the target system, for GDB.
   Copyright 1990, 1991, 1995 Free Software Foundation, Inc.
   Contributed by Cygnus Support.  Written by John Gilmore.

   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"

/* This file is only useful if BREAKPOINT is set.  If not, we punt.  */

#include "symtab.h"
#include "breakpoint.h"
#include "inferior.h"
#include "target.h"


/* Use the program counter to determine the contents and size
   of a breakpoint instruction.  If no target-dependent macro
   BREAKPOINT_FROM_PC has been defined to implement this function,
   assume that the breakpoint doesn't depend on the PC, and
   use the values of the BIG_BREAKPOINT and LITTLE_BREAKPOINT macros.
   Return a pointer to a string of bytes that encode a breakpoint
   instruction, stores the length of the string to *lenptr,
   and optionally adjust the pc to point to the correct memory location
   for inserting the breakpoint.  */

unsigned char *
memory_breakpoint_from_pc (pcptr, lenptr)
     CORE_ADDR *pcptr;
     int *lenptr;
{
  /* {BIG_,LITTLE_}BREAKPOINT is the sequence of bytes we insert for a
     breakpoint.  On some machines, breakpoints are handled by the
     target environment and we don't have to worry about them here.  */
#ifdef BIG_BREAKPOINT
  if (TARGET_BYTE_ORDER == BIG_ENDIAN)
    {
      static unsigned char big_break_insn[] = BIG_BREAKPOINT;
      *lenptr = sizeof (big_break_insn);
      return big_break_insn;
    }
#endif
#ifdef LITTLE_BREAKPOINT
  if (TARGET_BYTE_ORDER != BIG_ENDIAN)
    {
      static unsigned char little_break_insn[] = LITTLE_BREAKPOINT;
      *lenptr = sizeof (little_break_insn);
      return little_break_insn;
    }
#endif
#ifdef BREAKPOINT
  {
    static unsigned char break_insn[] = BREAKPOINT;
    *lenptr = sizeof (break_insn);
    return break_insn;
  }
#endif
  *lenptr = 0;
  return NULL;
}


/* Insert a breakpoint on targets that don't have any better breakpoint
   support.  We read the contents of the target location and stash it,
   then overwrite it with a breakpoint instruction.  ADDR is the target
   location in the target machine.  CONTENTS_CACHE is a pointer to 
   memory allocated for saving the target contents.  It is guaranteed
   by the caller to be long enough to save BREAKPOINT_LEN bytes (this
   is accomplished via BREAKPOINT_MAX).  */

int
default_memory_insert_breakpoint (addr, contents_cache)
     CORE_ADDR addr;
     char *contents_cache;
{
  int val;
  unsigned char *bp;
  int bplen;

  /* Determine appropriate breakpoint contents and size for this address.  */
  bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  if (bp == NULL)
    error ("Software breakpoints not implemented for this target.");

  /* Save the memory contents.  */
  val = target_read_memory (addr, contents_cache, bplen);

  /* Write the breakpoint.  */
  if (val == 0)
    val = target_write_memory (addr, (char *) bp, bplen);

  return val;
}


int
default_memory_remove_breakpoint (addr, contents_cache)
     CORE_ADDR addr;
     char *contents_cache;
{
  unsigned char *bp;
  int bplen;

  /* Determine appropriate breakpoint contents and size for this address.  */
  bp = BREAKPOINT_FROM_PC (&addr, &bplen);
  if (bp == NULL)
    error ("Software breakpoints not implemented for this target.");

  return target_write_memory (addr, contents_cache, bplen);
}


int
memory_insert_breakpoint (addr, contents_cache)
     CORE_ADDR addr;
     char *contents_cache;
{
  return MEMORY_INSERT_BREAKPOINT(addr, contents_cache);
}

int
memory_remove_breakpoint (addr, contents_cache)
     CORE_ADDR addr;
     char *contents_cache;
{
  return MEMORY_REMOVE_BREAKPOINT(addr, contents_cache);
}