aboutsummaryrefslogtreecommitdiff
path: root/gdb/mem-break.c
blob: 9bb4c454df0dbfa9da1a5d1df90bd891eb5b7d11 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* Simulate breakpoints by patching locations in the target system, for GDB.

   Copyright (C) 1990-2016 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 3 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, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "symtab.h"
#include "breakpoint.h"
#include "inferior.h"
#include "target.h"
/* 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.
   BP_TGT->placed_address is the target location in the target
   machine.  BP_TGT->shadow_contents is some 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 (struct gdbarch *gdbarch,
				  struct bp_target_info *bp_tgt)
{
  CORE_ADDR addr = bp_tgt->reqstd_address;
  const unsigned char *bp;
  gdb_byte *readbuf;
  int bplen;
  int val;

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

  bp_tgt->placed_address = addr;
  bp_tgt->placed_size = bplen;

  /* Save the memory contents in the shadow_contents buffer and then
     write the breakpoint instruction.  */
  readbuf = (gdb_byte *) alloca (bplen);
  val = target_read_memory (addr, readbuf, bplen);
  if (val == 0)
    {
      /* These must be set together, either before or after the shadow
	 read, so that if we're "reinserting" a breakpoint that
	 doesn't have a shadow yet, the breakpoint masking code inside
	 target_read_memory doesn't mask out this breakpoint using an
	 unfilled shadow buffer.  The core may be trying to reinsert a
	 permanent breakpoint, for targets that support breakpoint
	 conditions/commands on the target side for some types of
	 breakpoints, such as target remote.  */
      bp_tgt->shadow_len = bplen;
      memcpy (bp_tgt->shadow_contents, readbuf, bplen);

      val = target_write_raw_memory (addr, bp, bplen);
    }

  return val;
}


int
default_memory_remove_breakpoint (struct gdbarch *gdbarch,
				  struct bp_target_info *bp_tgt)
{
  return target_write_raw_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
				  bp_tgt->placed_size);
}


int
memory_insert_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
			  struct bp_target_info *bp_tgt)
{
  return gdbarch_memory_insert_breakpoint (gdbarch, bp_tgt);
}

int
memory_remove_breakpoint (struct target_ops *ops, struct gdbarch *gdbarch,
			  struct bp_target_info *bp_tgt)
{
  return gdbarch_memory_remove_breakpoint (gdbarch, bp_tgt);
}

int
memory_validate_breakpoint (struct gdbarch *gdbarch,
			    struct bp_target_info *bp_tgt)
{
  CORE_ADDR addr = bp_tgt->placed_address;
  const gdb_byte *bp;
  int val;
  int bplen;
  gdb_byte cur_contents[BREAKPOINT_MAX];
  struct cleanup *cleanup;
  int ret;

  /* Determine appropriate breakpoint contents and size for this
     address.  */
  bp = gdbarch_breakpoint_from_pc (gdbarch, &addr, &bplen);

  if (bp == NULL || bp_tgt->placed_size != bplen)
    return 0;

  /* Make sure we see the memory breakpoints.  */
  cleanup = make_show_memory_breakpoints_cleanup (1);
  val = target_read_memory (addr, cur_contents, bplen);

  /* If our breakpoint is no longer at the address, this means that
     the program modified the code on us, so it is wrong to put back
     the old value.  */
  ret = (val == 0 && memcmp (bp, cur_contents, bplen) == 0);

  do_cleanups (cleanup);
  return ret;
}