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 #include "symtab.h"
  24 #include "breakpoint.h"
  25 #include "inferior.h"
  26 #include "target.h"
  27 #include "gdb_string.h"
  28
  29
  30 /* Insert a breakpoint on targets that don't have any better
  31    breakpoint support.  We read the contents of the target location
  32    and stash it, then overwrite it with a breakpoint instruction.
  33    BP_TGT->placed_address is the target location in the target
  34    machine.  BP_TGT->shadow_contents is some memory allocated for
  35    saving the target contents.  It is guaranteed by the caller to be
  36    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  37    BREAKPOINT_MAX).  */
  38
  39 int
  40 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  41                                   struct bp_target_info *bp_tgt)
  42 {
  43   int val;
  44   const unsigned char *bp;
  45   gdb_byte *readbuf;
  46
  47   /* Determine appropriate breakpoint contents and size for this address.  */
  48   bp = gdbarch_breakpoint_from_pc
  49        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
  50   if (bp == NULL)
  51     error (_("Software breakpoints not implemented for this target."));
  52
  53   /* Save the memory contents in the shadow_contents buffer and then
  54      write the breakpoint instruction.  */
  55   bp_tgt->shadow_len = bp_tgt->placed_size;
  56   readbuf = alloca (bp_tgt->placed_size);
  57   val = target_read_memory (bp_tgt->placed_address, readbuf,
  58                             bp_tgt->placed_size);
  59   if (val == 0)
  60     {
  61       memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
  62       val = target_write_raw_memory (bp_tgt->placed_address, bp,
  63                                      bp_tgt->placed_size);
  64     }
  65
  66   return val;
  67 }
  68
  69
  70 int
  71 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  72                                   struct bp_target_info *bp_tgt)
  73 {
  74   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  75                                   bp_tgt->placed_size);
  76 }
  77
  78
  79 int
  80 memory_insert_breakpoint (struct gdbarch *gdbarch,
  81                           struct bp_target_info *bp_tgt)
  82 {
  83   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  84 }
  85
  86 int
  87 memory_remove_breakpoint (struct gdbarch *gdbarch,
  88                           struct bp_target_info *bp_tgt)
  89 {
  90   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  91 }