gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-2013 Free Software Foundation, Inc.
   4
   5    Contributed by Cygnus Support.  Written by John Gilmore.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23
  24 /* This file is only useful if BREAKPOINT_FROM_PC is set.  If not, we
  25    punt.  */
  26
  27 #include "symtab.h"
  28 #include "breakpoint.h"
  29 #include "inferior.h"
  30 #include "target.h"
  31 #include "gdb_string.h"
  32
  33
  34 /* Insert a breakpoint on targets that don't have any better
  35    breakpoint support.  We read the contents of the target location
  36    and stash it, then overwrite it with a breakpoint instruction.
  37    BP_TGT->placed_address is the target location in the target
  38    machine.  BP_TGT->shadow_contents is some memory allocated for
  39    saving the target contents.  It is guaranteed by the caller to be
  40    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  41    BREAKPOINT_MAX).  */
  42
  43 int
  44 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  45                                   struct bp_target_info *bp_tgt)
  46 {
  47   int val;
  48   const unsigned char *bp;
  49   gdb_byte *readbuf;
  50
  51   /* Determine appropriate breakpoint contents and size for this address.  */
  52   bp = gdbarch_breakpoint_from_pc
  53        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
  54   if (bp == NULL)
  55     error (_("Software breakpoints not implemented for this target."));
  56
  57   /* Save the memory contents in the shadow_contents buffer and then
  58      write the breakpoint instruction.  */
  59   bp_tgt->shadow_len = bp_tgt->placed_size;
  60   readbuf = alloca (bp_tgt->placed_size);
  61   val = target_read_memory (bp_tgt->placed_address, readbuf,
  62                             bp_tgt->placed_size);
  63   if (val == 0)
  64     {
  65       memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
  66       val = target_write_raw_memory (bp_tgt->placed_address, bp,
  67                                      bp_tgt->placed_size);
  68     }
  69
  70   return val;
  71 }
  72
  73
  74 int
  75 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  76                                   struct bp_target_info *bp_tgt)
  77 {
  78   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  79                                   bp_tgt->placed_size);
  80 }
  81
  82
  83 int
  84 memory_insert_breakpoint (struct gdbarch *gdbarch,
  85                           struct bp_target_info *bp_tgt)
  86 {
  87   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  88 }
  89
  90 int
  91 memory_remove_breakpoint (struct gdbarch *gdbarch,
  92                           struct bp_target_info *bp_tgt)
  93 {
  94   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  95 }