aboutsummaryrefslogtreecommitdiff
path: root/gdb/x86-nat.c
blob: f73dd1b24e47c638b5094997a14913c18750b5c5 (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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
/* Native-dependent code for x86 (i386 and x86-64).

   Copyright (C) 2001-2020 Free Software Foundation, Inc.

   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 "x86-nat.h"
#include "gdbcmd.h"
#include "inferior.h"

/* Support for hardware watchpoints and breakpoints using the x86
   debug registers.

   This provides several functions for inserting and removing
   hardware-assisted breakpoints and watchpoints, testing if one or
   more of the watchpoints triggered and at what address, checking
   whether a given region can be watched, etc.

   The functions below implement debug registers sharing by reference
   counts, and allow to watch regions up to 16 bytes long.  */

/* Low-level function vector.  */
struct x86_dr_low_type x86_dr_low;

/* Per-process data.  We don't bind this to a per-inferior registry
   because of targets like x86 GNU/Linux that need to keep track of
   processes that aren't bound to any inferior (e.g., fork children,
   checkpoints).  */

struct x86_process_info
{
  /* Linked list.  */
  struct x86_process_info *next;

  /* The process identifier.  */
  pid_t pid;

  /* Copy of x86 hardware debug registers.  */
  struct x86_debug_reg_state state;
};

static struct x86_process_info *x86_process_list = NULL;

/* Find process data for process PID.  */

static struct x86_process_info *
x86_find_process_pid (pid_t pid)
{
  struct x86_process_info *proc;

  for (proc = x86_process_list; proc; proc = proc->next)
    if (proc->pid == pid)
      return proc;

  return NULL;
}

/* Add process data for process PID.  Returns newly allocated info
   object.  */

static struct x86_process_info *
x86_add_process (pid_t pid)
{
  struct x86_process_info *proc = XCNEW (struct x86_process_info);

  proc->pid = pid;
  proc->next = x86_process_list;
  x86_process_list = proc;

  return proc;
}

/* Get data specific info for process PID, creating it if necessary.
   Never returns NULL.  */

static struct x86_process_info *
x86_process_info_get (pid_t pid)
{
  struct x86_process_info *proc;

  proc = x86_find_process_pid (pid);
  if (proc == NULL)
    proc = x86_add_process (pid);

  return proc;
}

/* Get debug registers state for process PID.  */

struct x86_debug_reg_state *
x86_debug_reg_state (pid_t pid)
{
  return &x86_process_info_get (pid)->state;
}

/* See declaration in x86-nat.h.  */

void
x86_forget_process (pid_t pid)
{
  struct x86_process_info *proc, **proc_link;

  proc = x86_process_list;
  proc_link = &x86_process_list;

  while (proc != NULL)
    {
      if (proc->pid == pid)
	{
	  *proc_link = proc->next;

	  xfree (proc);
	  return;
	}

      proc_link = &proc->next;
      proc = *proc_link;
    }
}

/* Clear the reference counts and forget everything we knew about the
   debug registers.  */

void
x86_cleanup_dregs (void)
{
  /* Starting from scratch has the same effect.  */
  x86_forget_process (inferior_ptid.pid ());
}

/* Insert a watchpoint to watch a memory region which starts at
   address ADDR and whose length is LEN bytes.  Watch memory accesses
   of the type TYPE.  Return 0 on success, -1 on failure.  */

int
x86_insert_watchpoint (CORE_ADDR addr, int len,
		       enum target_hw_bp_type type, struct expression *cond)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_insert_watchpoint (state, type, addr, len);
}

/* Remove a watchpoint that watched the memory region which starts at
   address ADDR, whose length is LEN bytes, and for accesses of the
   type TYPE.  Return 0 on success, -1 on failure.  */
int
x86_remove_watchpoint (CORE_ADDR addr, int len,
		       enum target_hw_bp_type type, struct expression *cond)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_remove_watchpoint (state, type, addr, len);
}

/* Return non-zero if we can watch a memory region that starts at
   address ADDR and whose length is LEN bytes.  */

int
x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_region_ok_for_watchpoint (state, addr, len);
}

/* If the inferior has some break/watchpoint that triggered, set the
   address associated with that break/watchpoint and return non-zero.
   Otherwise, return zero.  */

int
x86_stopped_data_address (CORE_ADDR *addr_p)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_stopped_data_address (state, addr_p);
}

/* Return non-zero if the inferior has some watchpoint that triggered.
   Otherwise return zero.  */

int
x86_stopped_by_watchpoint ()
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_stopped_by_watchpoint (state);
}

/* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
   Return 0 on success, EBUSY on failure.  */

int
x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  bp_tgt->placed_address = bp_tgt->reqstd_address;
  return x86_dr_insert_watchpoint (state, hw_execute,
				   bp_tgt->placed_address, 1) ? EBUSY : 0;
}

/* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
   Return 0 on success, -1 on failure.  */

int
x86_remove_hw_breakpoint (struct gdbarch *gdbarch,
			  struct bp_target_info *bp_tgt)
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_remove_watchpoint (state, hw_execute,
				   bp_tgt->placed_address, 1);
}

/* Returns the number of hardware watchpoints of type TYPE that we can
   set.  Value is positive if we can set CNT watchpoints, zero if
   setting watchpoints of type TYPE is not supported, and negative if
   CNT is more than the maximum number of watchpoints of type TYPE
   that we can support.  TYPE is one of bp_hardware_watchpoint,
   bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
   CNT is the number of such watchpoints used so far (including this
   one).  OTHERTYPE is non-zero if other types of watchpoints are
   currently enabled.

   We always return 1 here because we don't have enough information
   about possible overlap of addresses that they want to watch.  As an
   extreme example, consider the case where all the watchpoints watch
   the same address and the same region length: then we can handle a
   virtually unlimited number of watchpoints, due to debug register
   sharing implemented via reference counts in x86-nat.c.  */

int
x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype)
{
  return 1;
}

/* Return non-zero if the inferior has some breakpoint that triggered.
   Otherwise return zero.  */

int
x86_stopped_by_hw_breakpoint ()
{
  struct x86_debug_reg_state *state
    = x86_debug_reg_state (inferior_ptid.pid ());

  return x86_dr_stopped_by_hw_breakpoint (state);
}

static void
add_show_debug_regs_command (void)
{
  /* A maintenance command to enable printing the internal DRi mirror
     variables.  */
  add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
			   &show_debug_regs, _("\
Set whether to show variables that mirror the x86 debug registers."), _("\
Show whether to show variables that mirror the x86 debug registers."), _("\
Use \"on\" to enable, \"off\" to disable.\n\
If enabled, the debug registers values are shown when GDB inserts\n\
or removes a hardware breakpoint or watchpoint, and when the inferior\n\
triggers a breakpoint or watchpoint."),
			   NULL,
			   NULL,
			   &maintenance_set_cmdlist,
			   &maintenance_show_cmdlist);
}

/* See x86-nat.h.  */

void
x86_set_debug_register_length (int len)
{
  /* This function should be called only once for each native target.  */
  gdb_assert (x86_dr_low.debug_register_length == 0);
  gdb_assert (len == 4 || len == 8);
  x86_dr_low.debug_register_length = len;
  add_show_debug_regs_command ();
}