gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-1993, 1995, 1997-2000, 2002, 2007-2012 Free
   4    Software Foundation, Inc.
   5
   6    Contributed by Cygnus Support.  Written by John Gilmore.
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  22
  23 #include "defs.h"
  24
  25 /* This file is only useful if BREAKPOINT_FROM_PC is set.  If not, we
  26    punt.  */
  27
  28 #include "symtab.h"
  29 #include "breakpoint.h"
  30 #include "inferior.h"
  31 #include "target.h"
  32 #include "gdb_string.h"
  33
  34
  35 /* Insert a breakpoint on targets that don't have any better
  36    breakpoint support.  We read the contents of the target location
  37    and stash it, then overwrite it with a breakpoint instruction.
  38    BP_TGT->placed_address is the target location in the target
  39    machine.  BP_TGT->shadow_contents is some memory allocated for
  40    saving the target contents.  It is guaranteed by the caller to be
  41    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  42    BREAKPOINT_MAX).  */
  43
  44 int
  45 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  46                                   struct bp_target_info *bp_tgt)
  47 {
  48   int val;
  49   const unsigned char *bp;
  50   gdb_byte *readbuf;
  51
  52   /* Determine appropriate breakpoint contents and size for this address.  */
  53   bp = gdbarch_breakpoint_from_pc
  54        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
  55   if (bp == NULL)
  56     error (_("Software breakpoints not implemented for this target."));
  57
  58   /* Save the memory contents in the shadow_contents buffer and then
  59      write the breakpoint instruction.  */
  60   bp_tgt->shadow_len = bp_tgt->placed_size;
  61   readbuf = alloca (bp_tgt->placed_size);
  62   val = target_read_memory (bp_tgt->placed_address, readbuf,
  63                             bp_tgt->placed_size);
  64   if (val == 0)
  65     {
  66       memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
  67       val = target_write_raw_memory (bp_tgt->placed_address, bp,
  68                                      bp_tgt->placed_size);
  69     }
  70
  71   return val;
  72 }
  73
  74
  75 int
  76 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  77                                   struct bp_target_info *bp_tgt)
  78 {
  79   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  80                                   bp_tgt->placed_size);
  81 }
  82
  83
  84 int
  85 memory_insert_breakpoint (struct gdbarch *gdbarch,
  86                           struct bp_target_info *bp_tgt)
  87 {
  88   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  89 }
  90
  91 int
  92 memory_remove_breakpoint (struct gdbarch *gdbarch,
  93                           struct bp_target_info *bp_tgt)
  94 {
  95   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  96 }