gdb/mem-break.c

   1 /* Simulate breakpoints by patching locations in the target system, for GDB.
   2
   3    Copyright (C) 1990-2014 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 /* Insert a breakpoint on targets that don't have any better
  28    breakpoint support.  We read the contents of the target location
  29    and stash it, then overwrite it with a breakpoint instruction.
  30    BP_TGT->placed_address is the target location in the target
  31    machine.  BP_TGT->shadow_contents is some memory allocated for
  32    saving the target contents.  It is guaranteed by the caller to be
  33    long enough to save BREAKPOINT_LEN bytes (this is accomplished via
  34    BREAKPOINT_MAX).  */
  35
  36 int
  37 default_memory_insert_breakpoint (struct gdbarch *gdbarch,
  38                                   struct bp_target_info *bp_tgt)
  39 {
  40   int val;
  41   const unsigned char *bp;
  42   gdb_byte *readbuf;
  43
  44   /* Determine appropriate breakpoint contents and size for this address.  */
  45   bp = gdbarch_breakpoint_from_pc
  46        (gdbarch, &bp_tgt->placed_address, &bp_tgt->placed_size);
  47   if (bp == NULL)
  48     error (_("Software breakpoints not implemented for this target."));
  49
  50   /* Save the memory contents in the shadow_contents buffer and then
  51      write the breakpoint instruction.  */
  52   bp_tgt->shadow_len = bp_tgt->placed_size;
  53   readbuf = alloca (bp_tgt->placed_size);
  54   val = target_read_memory (bp_tgt->placed_address, readbuf,
  55                             bp_tgt->placed_size);
  56   if (val == 0)
  57     {
  58       memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
  59       val = target_write_raw_memory (bp_tgt->placed_address, bp,
  60                                      bp_tgt->placed_size);
  61     }
  62
  63   return val;
  64 }
  65
  66
  67 int
  68 default_memory_remove_breakpoint (struct gdbarch *gdbarch,
  69                                   struct bp_target_info *bp_tgt)
  70 {
  71   return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
  72                                   bp_tgt->placed_size);
  73 }
  74
  75
  76 int
  77 memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  78                           struct bp_target_info *bp_tgt)
  79 {
  80   return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
  81 }
  82
  83 int
  84 memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
  85                           struct bp_target_info *bp_tgt)
  86 {
  87   return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
  88 }
  89
  90 int
  91 memory_validate_breakpoint (struct gdbarch *gdbarch,
  92                             struct bp_target_info *bp_tgt)
  93 {
  94   CORE_ADDR addr = bp_tgt->placed_address;
  95   const gdb_byte *bp;
  96   int val;
  97   int bplen;
  98   gdb_byte cur_contents[BREAKPOINT_MAX];
  99   struct cleanup *cleanup;
 100   int ret;
 101
 102   /* Determine appropriate breakpoint contents and size for this
 103      address.  */
 104   bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);
 105
 106   if (bp == NULL || bp_tgt->placed_size != bplen)
 107     return 0;
 108
 109   /* Make sure we see the memory breakpoints.  */
 110   cleanup = make_show_memory_breakpoints_cleanup (1);
 111   val = target_read_memory (addr, cur_contents, bplen);
 112
 113   /* If our breakpoint is no longer at the address, this means that
 114      the program modified the code on us, so it is wrong to put back
 115      the old value.  */
 116   ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);
 117
 118   do_cleanups (cleanup);
 119   return ret;
 120 }