gdb/i386-nat.c

   1 /* Native-dependent code for the i386.
   2
   3    Copyright (C) 2001-2014 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 "i386-nat.h"
  22 #include "gdbcmd.h"
  23 #include "inferior.h"
  24
  25 /* Support for hardware watchpoints and breakpoints using the i386
  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 /* Whether or not to print the mirrored debug registers.  */
  37 int debug_hw_points;
  38
  39 /* Low-level function vector.  */
  40 struct i386_dr_low_type i386_dr_low;
  41
  42 /* Per-process data.  We don't bind this to a per-inferior registry
  43    because of targets like x86 GNU/Linux that need to keep track of
  44    processes that aren't bound to any inferior (e.g., fork children,
  45    checkpoints).  */
  46
  47 struct i386_process_info
  48 {
  49   /* Linked list.  */
  50   struct i386_process_info *next;
  51
  52   /* The process identifier.  */
  53   pid_t pid;
  54
  55   /* Copy of i386 hardware debug registers.  */
  56   struct i386_debug_reg_state state;
  57 };
  58
  59 static struct i386_process_info *i386_process_list = NULL;
  60
  61 /* Find process data for process PID.  */
  62
  63 static struct i386_process_info *
  64 i386_find_process_pid (pid_t pid)
  65 {
  66   struct i386_process_info *proc;
  67
  68   for (proc = i386_process_list; proc; proc = proc->next)
  69     if (proc->pid == pid)
  70       return proc;
  71
  72   return NULL;
  73 }
  74
  75 /* Add process data for process PID.  Returns newly allocated info
  76    object.  */
  77
  78 static struct i386_process_info *
  79 i386_add_process (pid_t pid)
  80 {
  81   struct i386_process_info *proc;
  82
  83   proc = xcalloc (1, sizeof (*proc));
  84   proc->pid = pid;
  85
  86   proc->next = i386_process_list;
  87   i386_process_list = proc;
  88
  89   return proc;
  90 }
  91
  92 /* Get data specific info for process PID, creating it if necessary.
  93    Never returns NULL.  */
  94
  95 static struct i386_process_info *
  96 i386_process_info_get (pid_t pid)
  97 {
  98   struct i386_process_info *proc;
  99
 100   proc = i386_find_process_pid (pid);
 101   if (proc == NULL)
 102     proc = i386_add_process (pid);
 103
 104   return proc;
 105 }
 106
 107 /* Get debug registers state for process PID.  */
 108
 109 struct i386_debug_reg_state *
 110 i386_debug_reg_state (pid_t pid)
 111 {
 112   return &i386_process_info_get (pid)->state;
 113 }
 114
 115 /* See declaration in i386-nat.h.  */
 116
 117 void
 118 i386_forget_process (pid_t pid)
 119 {
 120   struct i386_process_info *proc, **proc_link;
 121
 122   proc = i386_process_list;
 123   proc_link = &i386_process_list;
 124
 125   while (proc != NULL)
 126     {
 127       if (proc->pid == pid)
 128         {
 129           *proc_link = proc->next;
 130
 131           xfree (proc);
 132           return;
 133         }
 134
 135       proc_link = &proc->next;
 136       proc = *proc_link;
 137     }
 138 }
 139
 140 /* Clear the reference counts and forget everything we knew about the
 141    debug registers.  */
 142
 143 void
 144 i386_cleanup_dregs (void)
 145 {
 146   /* Starting from scratch has the same effect.  */
 147   i386_forget_process (ptid_get_pid (inferior_ptid));
 148 }
 149
 150 /* Insert a watchpoint to watch a memory region which starts at
 151    address ADDR and whose length is LEN bytes.  Watch memory accesses
 152    of the type TYPE.  Return 0 on success, -1 on failure.  */
 153
 154 static int
 155 i386_insert_watchpoint (struct target_ops *self,
 156                         CORE_ADDR addr, int len, int type,
 157                         struct expression *cond)
 158 {
 159   struct i386_debug_reg_state *state
 160     = i386_debug_reg_state (ptid_get_pid (inferior_ptid));
 161
 162   return i386_dr_insert_watchpoint (state, type, addr, len);
 163 }
 164
 165 /* Remove a watchpoint that watched the memory region which starts at
 166    address ADDR, whose length is LEN bytes, and for accesses of the
 167    type TYPE.  Return 0 on success, -1 on failure.  */
 168 static int
 169 i386_remove_watchpoint (struct target_ops *self,
 170                         CORE_ADDR addr, int len, int type,
 171                         struct expression *cond)
 172 {
 173   struct i386_debug_reg_state *state
 174     = i386_debug_reg_state (ptid_get_pid (inferior_ptid));
 175
 176   return i386_dr_remove_watchpoint (state, type, addr, len);
 177 }
 178
 179 /* Return non-zero if we can watch a memory region that starts at
 180    address ADDR and whose length is LEN bytes.  */
 181
 182 static int
 183 i386_region_ok_for_watchpoint (struct target_ops *self,
 184                                CORE_ADDR addr, int len)
 185 {
 186   struct i386_debug_reg_state *state
 187     = i386_debug_reg_state (ptid_get_pid (inferior_ptid));
 188
 189   return i386_dr_region_ok_for_watchpoint (state, addr, len);
 190 }
 191
 192 /* If the inferior has some break/watchpoint that triggered, set the
 193    address associated with that break/watchpoint and return non-zero.
 194    Otherwise, return zero.  */
 195
 196 static int
 197 i386_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p)
 198 {
 199   struct i386_debug_reg_state *state
 200     = i386_debug_reg_state (ptid_get_pid (inferior_ptid));
 201
 202   return i386_dr_stopped_data_address (state, addr_p);
 203 }
 204
 205 /* Return non-zero if the inferior has some watchpoint that triggered.
 206    Otherwise return zero.  */
 207
 208 static int
 209 i386_stopped_by_watchpoint (struct target_ops *ops)
 210 {
 211   CORE_ADDR addr = 0;
 212   return i386_stopped_data_address (ops, &addr);
 213 }
 214
 215 /* Insert a hardware-assisted breakpoint at BP_TGT->placed_address.
 216    Return 0 on success, EBUSY on failure.  */
 217
 218 static int
 219 i386_insert_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 220                            struct bp_target_info *bp_tgt)
 221 {
 222   return i386_insert_watchpoint (self, bp_tgt->placed_address, 1,
 223                                  hw_execute, NULL) ? EBUSY : 0;
 224 }
 225
 226 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
 227    Return 0 on success, -1 on failure.  */
 228
 229 static int
 230 i386_remove_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 231                            struct bp_target_info *bp_tgt)
 232 {
 233   return i386_remove_watchpoint (self, bp_tgt->placed_address, 1,
 234                                  hw_execute, NULL);
 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 i386-nat.c.  */
 253
 254 static int
 255 i386_can_use_hw_breakpoint (struct target_ops *self,
 256                             int type, int cnt, int othertype)
 257 {
 258   return 1;
 259 }
 260
 261 static void
 262 add_show_debug_regs_command (void)
 263 {
 264   /* A maintenance command to enable printing the internal DRi mirror
 265      variables.  */
 266   add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
 267                            &debug_hw_points, _("\
 268 Set whether to show variables that mirror the x86 debug registers."), _("\
 269 Show whether to show variables that mirror the x86 debug registers."), _("\
 270 Use \"on\" to enable, \"off\" to disable.\n\
 271 If enabled, the debug registers values are shown when GDB inserts\n\
 272 or removes a hardware breakpoint or watchpoint, and when the inferior\n\
 273 triggers a breakpoint or watchpoint."),
 274                            NULL,
 275                            NULL,
 276                            &maintenance_set_cmdlist,
 277                            &maintenance_show_cmdlist);
 278 }
 279
 280 /* There are only two global functions left.  */
 281
 282 void
 283 i386_use_watchpoints (struct target_ops *t)
 284 {
 285   /* After a watchpoint trap, the PC points to the instruction after the
 286      one that caused the trap.  Therefore we don't need to step over it.
 287      But we do need to reset the status register to avoid another trap.  */
 288   t->to_have_continuable_watchpoint = 1;
 289
 290   t->to_can_use_hw_breakpoint = i386_can_use_hw_breakpoint;
 291   t->to_region_ok_for_hw_watchpoint = i386_region_ok_for_watchpoint;
 292   t->to_stopped_by_watchpoint = i386_stopped_by_watchpoint;
 293   t->to_stopped_data_address = i386_stopped_data_address;
 294   t->to_insert_watchpoint = i386_insert_watchpoint;
 295   t->to_remove_watchpoint = i386_remove_watchpoint;
 296   t->to_insert_hw_breakpoint = i386_insert_hw_breakpoint;
 297   t->to_remove_hw_breakpoint = i386_remove_hw_breakpoint;
 298 }
 299
 300 void
 301 i386_set_debug_register_length (int len)
 302 {
 303   /* This function should be called only once for each native target.  */
 304   gdb_assert (i386_dr_low.debug_register_length == 0);
 305   gdb_assert (len == 4 || len == 8);
 306   i386_dr_low.debug_register_length = len;
 307   add_show_debug_regs_command ();
 308 }