1/* Native-dependent code for x86 (i386 and x86-64).
2
3   Copyright (C) 2001-2020 Free Software Foundation, Inc.
4
5   This file is part of GDB.
6
7   This program is free software; you can redistribute it and/or modify
8   it under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3 of the License, or
10   (at your option) any later version.
11
12   This program is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   GNU General Public License for more details.
16
17   You should have received a copy of the GNU General Public License
18   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
19
20#include "defs.h"
21#include "x86-nat.h"
22#include "gdbcmd.h"
23#include "inferior.h"
24
25/* Support for hardware watchpoints and breakpoints using the x86
26   debug registers.
27
28   This provides several functions for inserting and removing
29   hardware-assisted breakpoints and watchpoints, testing if one or
30   more of the watchpoints triggered and at what address, checking
31   whether a given region can be watched, etc.
32
33   The functions below implement debug registers sharing by reference
34   counts, and allow to watch regions up to 16 bytes long.  */
35
36/* Low-level function vector.  */
37struct x86_dr_low_type x86_dr_low;
38
39/* Per-process data.  We don't bind this to a per-inferior registry
40   because of targets like x86 GNU/Linux that need to keep track of
41   processes that aren't bound to any inferior (e.g., fork children,
42   checkpoints).  */
43
44struct x86_process_info
45{
46  /* Linked list.  */
47  struct x86_process_info *next;
48
49  /* The process identifier.  */
50  pid_t pid;
51
52  /* Copy of x86 hardware debug registers.  */
53  struct x86_debug_reg_state state;
54};
55
56static struct x86_process_info *x86_process_list = NULL;
57
58/* Find process data for process PID.  */
59
60static struct x86_process_info *
61x86_find_process_pid (pid_t pid)
62{
63  struct x86_process_info *proc;
64
65  for (proc = x86_process_list; proc; proc = proc->next)
66    if (proc->pid == pid)
67      return proc;
68
69  return NULL;
70}
71
72/* Add process data for process PID.  Returns newly allocated info
73   object.  */
74
75static struct x86_process_info *
76x86_add_process (pid_t pid)
77{
78  struct x86_process_info *proc = XCNEW (struct x86_process_info);
79
80  proc->pid = pid;
81  proc->next = x86_process_list;
82  x86_process_list = proc;
83
84  return proc;
85}
86
87/* Get data specific info for process PID, creating it if necessary.
88   Never returns NULL.  */
89
90static struct x86_process_info *
91x86_process_info_get (pid_t pid)
92{
93  struct x86_process_info *proc;
94
95  proc = x86_find_process_pid (pid);
96  if (proc == NULL)
97    proc = x86_add_process (pid);
98
99  return proc;
100}
101
102/* Get debug registers state for process PID.  */
103
104struct x86_debug_reg_state *
105x86_debug_reg_state (pid_t pid)
106{
107  return &x86_process_info_get (pid)->state;
108}
109
110/* See declaration in x86-nat.h.  */
111
112void
113x86_forget_process (pid_t pid)
114{
115  struct x86_process_info *proc, **proc_link;
116
117  proc = x86_process_list;
118  proc_link = &x86_process_list;
119
120  while (proc != NULL)
121    {
122      if (proc->pid == pid)
123	{
124	  *proc_link = proc->next;
125
126	  xfree (proc);
127	  return;
128	}
129
130      proc_link = &proc->next;
131      proc = *proc_link;
132    }
133}
134
135/* Clear the reference counts and forget everything we knew about the
136   debug registers.  */
137
138void
139x86_cleanup_dregs (void)
140{
141  /* Starting from scratch has the same effect.  */
142  x86_forget_process (inferior_ptid.pid ());
143}
144
145/* Insert a watchpoint to watch a memory region which starts at
146   address ADDR and whose length is LEN bytes.  Watch memory accesses
147   of the type TYPE.  Return 0 on success, -1 on failure.  */
148
149int
150x86_insert_watchpoint (CORE_ADDR addr, int len,
151		       enum target_hw_bp_type type, struct expression *cond)
152{
153  struct x86_debug_reg_state *state
154    = x86_debug_reg_state (inferior_ptid.pid ());
155
156  return x86_dr_insert_watchpoint (state, type, addr, len);
157}
158
159/* Remove a watchpoint that watched the memory region which starts at
160   address ADDR, whose length is LEN bytes, and for accesses of the
161   type TYPE.  Return 0 on success, -1 on failure.  */
162int
163x86_remove_watchpoint (CORE_ADDR addr, int len,
164		       enum target_hw_bp_type type, struct expression *cond)
165{
166  struct x86_debug_reg_state *state
167    = x86_debug_reg_state (inferior_ptid.pid ());
168
169  return x86_dr_remove_watchpoint (state, type, addr, len);
170}
171
172/* Return non-zero if we can watch a memory region that starts at
173   address ADDR and whose length is LEN bytes.  */
174
175int
176x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
177{
178  struct x86_debug_reg_state *state
179    = x86_debug_reg_state (inferior_ptid.pid ());
180
181  return x86_dr_region_ok_for_watchpoint (state, addr, len);
182}
183
184/* If the inferior has some break/watchpoint that triggered, set the
185   address associated with that break/watchpoint and return non-zero.
186   Otherwise, return zero.  */
187
188int
189x86_stopped_data_address (CORE_ADDR *addr_p)
190{
191  struct x86_debug_reg_state *state
192    = x86_debug_reg_state (inferior_ptid.pid ());
193
194  return x86_dr_stopped_data_address (state, addr_p);
195}
196
197/* Return non-zero if the inferior has some watchpoint that triggered.
198   Otherwise return zero.  */
199
200int
201x86_stopped_by_watchpoint ()
202{
203  struct x86_debug_reg_state *state
204    = x86_debug_reg_state (inferior_ptid.pid ());
205
206  return x86_dr_stopped_by_watchpoint (state);
207}
208
209/* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
210   Return 0 on success, EBUSY on failure.  */
211
212int
213x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt)
214{
215  struct x86_debug_reg_state *state
216    = x86_debug_reg_state (inferior_ptid.pid ());
217
218  bp_tgt->placed_address = bp_tgt->reqstd_address;
219  return x86_dr_insert_watchpoint (state, hw_execute,
220				   bp_tgt->placed_address, 1) ? EBUSY : 0;
221}
222
223/* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
224   Return 0 on success, -1 on failure.  */
225
226int
227x86_remove_hw_breakpoint (struct gdbarch *gdbarch,
228			  struct bp_target_info *bp_tgt)
229{
230  struct x86_debug_reg_state *state
231    = x86_debug_reg_state (inferior_ptid.pid ());
232
233  return x86_dr_remove_watchpoint (state, hw_execute,
234				   bp_tgt->placed_address, 1);
235}
236
237/* Returns the number of hardware watchpoints of type TYPE that we can
238   set.  Value is positive if we can set CNT watchpoints, zero if
239   setting watchpoints of type TYPE is not supported, and negative if
240   CNT is more than the maximum number of watchpoints of type TYPE
241   that we can support.  TYPE is one of bp_hardware_watchpoint,
242   bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
243   CNT is the number of such watchpoints used so far (including this
244   one).  OTHERTYPE is non-zero if other types of watchpoints are
245   currently enabled.
246
247   We always return 1 here because we don't have enough information
248   about possible overlap of addresses that they want to watch.  As an
249   extreme example, consider the case where all the watchpoints watch
250   the same address and the same region length: then we can handle a
251   virtually unlimited number of watchpoints, due to debug register
252   sharing implemented via reference counts in x86-nat.c.  */
253
254int
255x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype)
256{
257  return 1;
258}
259
260/* Return non-zero if the inferior has some breakpoint that triggered.
261   Otherwise return zero.  */
262
263int
264x86_stopped_by_hw_breakpoint ()
265{
266  struct x86_debug_reg_state *state
267    = x86_debug_reg_state (inferior_ptid.pid ());
268
269  return x86_dr_stopped_by_hw_breakpoint (state);
270}
271
272static void
273add_show_debug_regs_command (void)
274{
275  /* A maintenance command to enable printing the internal DRi mirror
276     variables.  */
277  add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
278			   &show_debug_regs, _("\
279Set whether to show variables that mirror the x86 debug registers."), _("\
280Show whether to show variables that mirror the x86 debug registers."), _("\
281Use \"on\" to enable, \"off\" to disable.\n\
282If enabled, the debug registers values are shown when GDB inserts\n\
283or removes a hardware breakpoint or watchpoint, and when the inferior\n\
284triggers a breakpoint or watchpoint."),
285			   NULL,
286			   NULL,
287			   &maintenance_set_cmdlist,
288			   &maintenance_show_cmdlist);
289}
290
291/* See x86-nat.h.  */
292
293void
294x86_set_debug_register_length (int len)
295{
296  /* This function should be called only once for each native target.  */
297  gdb_assert (x86_dr_low.debug_register_length == 0);
298  gdb_assert (len == 4 || len == 8);
299  x86_dr_low.debug_register_length = len;
300  add_show_debug_regs_command ();
301}
302