gdb/x86-nat.c

   1 /* Native-dependent code for x86 (i386 and x86-64).
   2
   3    Copyright (C) 2001-2015 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.  */
  37 struct 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
  44 struct 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
  56 static struct x86_process_info *x86_process_list = NULL;
  57
  58 /* Find process data for process PID.  */
  59
  60 static struct x86_process_info *
  61 x86_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
  75 static struct x86_process_info *
  76 x86_add_process (pid_t pid)
  77 {
  78   struct x86_process_info *proc;
  79
  80   proc = xcalloc (1, sizeof (*proc));
  81   proc->pid = pid;
  82
  83   proc->next = x86_process_list;
  84   x86_process_list = proc;
  85
  86   return proc;
  87 }
  88
  89 /* Get data specific info for process PID, creating it if necessary.
  90    Never returns NULL.  */
  91
  92 static struct x86_process_info *
  93 x86_process_info_get (pid_t pid)
  94 {
  95   struct x86_process_info *proc;
  96
  97   proc = x86_find_process_pid (pid);
  98   if (proc == NULL)
  99     proc = x86_add_process (pid);
 100
 101   return proc;
 102 }
 103
 104 /* Get debug registers state for process PID.  */
 105
 106 struct x86_debug_reg_state *
 107 x86_debug_reg_state (pid_t pid)
 108 {
 109   return &x86_process_info_get (pid)->state;
 110 }
 111
 112 /* See declaration in i386-nat.h.  */
 113
 114 void
 115 x86_forget_process (pid_t pid)
 116 {
 117   struct x86_process_info *proc, **proc_link;
 118
 119   proc = x86_process_list;
 120   proc_link = &x86_process_list;
 121
 122   while (proc != NULL)
 123     {
 124       if (proc->pid == pid)
 125         {
 126           *proc_link = proc->next;
 127
 128           xfree (proc);
 129           return;
 130         }
 131
 132       proc_link = &proc->next;
 133       proc = *proc_link;
 134     }
 135 }
 136
 137 /* Clear the reference counts and forget everything we knew about the
 138    debug registers.  */
 139
 140 void
 141 x86_cleanup_dregs (void)
 142 {
 143   /* Starting from scratch has the same effect.  */
 144   x86_forget_process (ptid_get_pid (inferior_ptid));
 145 }
 146
 147 /* Insert a watchpoint to watch a memory region which starts at
 148    address ADDR and whose length is LEN bytes.  Watch memory accesses
 149    of the type TYPE.  Return 0 on success, -1 on failure.  */
 150
 151 static int
 152 x86_insert_watchpoint (struct target_ops *self,
 153                        CORE_ADDR addr, int len, int type,
 154                        struct expression *cond)
 155 {
 156   struct x86_debug_reg_state *state
 157     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 158
 159   return x86_dr_insert_watchpoint (state, type, addr, len);
 160 }
 161
 162 /* Remove a watchpoint that watched the memory region which starts at
 163    address ADDR, whose length is LEN bytes, and for accesses of the
 164    type TYPE.  Return 0 on success, -1 on failure.  */
 165 static int
 166 x86_remove_watchpoint (struct target_ops *self,
 167                        CORE_ADDR addr, int len, int type,
 168                        struct expression *cond)
 169 {
 170   struct x86_debug_reg_state *state
 171     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 172
 173   return x86_dr_remove_watchpoint (state, type, addr, len);
 174 }
 175
 176 /* Return non-zero if we can watch a memory region that starts at
 177    address ADDR and whose length is LEN bytes.  */
 178
 179 static int
 180 x86_region_ok_for_watchpoint (struct target_ops *self,
 181                               CORE_ADDR addr, int len)
 182 {
 183   struct x86_debug_reg_state *state
 184     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 185
 186   return x86_dr_region_ok_for_watchpoint (state, addr, len);
 187 }
 188
 189 /* If the inferior has some break/watchpoint that triggered, set the
 190    address associated with that break/watchpoint and return non-zero.
 191    Otherwise, return zero.  */
 192
 193 static int
 194 x86_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p)
 195 {
 196   struct x86_debug_reg_state *state
 197     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 198
 199   return x86_dr_stopped_data_address (state, addr_p);
 200 }
 201
 202 /* Return non-zero if the inferior has some watchpoint that triggered.
 203    Otherwise return zero.  */
 204
 205 static int
 206 x86_stopped_by_watchpoint (struct target_ops *ops)
 207 {
 208   struct x86_debug_reg_state *state
 209     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 210
 211   return x86_dr_stopped_by_watchpoint (state);
 212 }
 213
 214 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
 215    Return 0 on success, EBUSY on failure.  */
 216
 217 static int
 218 x86_insert_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 219                           struct bp_target_info *bp_tgt)
 220 {
 221   struct x86_debug_reg_state *state
 222     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 223
 224   bp_tgt->placed_address = bp_tgt->reqstd_address;
 225   return x86_dr_insert_watchpoint (state, hw_execute,
 226                                    bp_tgt->placed_address, 1) ? EBUSY : 0;
 227 }
 228
 229 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
 230    Return 0 on success, -1 on failure.  */
 231
 232 static int
 233 x86_remove_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 234                           struct bp_target_info *bp_tgt)
 235 {
 236   struct x86_debug_reg_state *state
 237     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 238
 239   return x86_dr_remove_watchpoint (state, hw_execute,
 240                                    bp_tgt->placed_address, 1);
 241 }
 242
 243 /* Returns the number of hardware watchpoints of type TYPE that we can
 244    set.  Value is positive if we can set CNT watchpoints, zero if
 245    setting watchpoints of type TYPE is not supported, and negative if
 246    CNT is more than the maximum number of watchpoints of type TYPE
 247    that we can support.  TYPE is one of bp_hardware_watchpoint,
 248    bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
 249    CNT is the number of such watchpoints used so far (including this
 250    one).  OTHERTYPE is non-zero if other types of watchpoints are
 251    currently enabled.
 252
 253    We always return 1 here because we don't have enough information
 254    about possible overlap of addresses that they want to watch.  As an
 255    extreme example, consider the case where all the watchpoints watch
 256    the same address and the same region length: then we can handle a
 257    virtually unlimited number of watchpoints, due to debug register
 258    sharing implemented via reference counts in i386-nat.c.  */
 259
 260 static int
 261 x86_can_use_hw_breakpoint (struct target_ops *self,
 262                            int type, int cnt, int othertype)
 263 {
 264   return 1;
 265 }
 266
 267 static void
 268 add_show_debug_regs_command (void)
 269 {
 270   /* A maintenance command to enable printing the internal DRi mirror
 271      variables.  */
 272   add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
 273                            &show_debug_regs, _("\
 274 Set whether to show variables that mirror the x86 debug registers."), _("\
 275 Show whether to show variables that mirror the x86 debug registers."), _("\
 276 Use \"on\" to enable, \"off\" to disable.\n\
 277 If enabled, the debug registers values are shown when GDB inserts\n\
 278 or removes a hardware breakpoint or watchpoint, and when the inferior\n\
 279 triggers a breakpoint or watchpoint."),
 280                            NULL,
 281                            NULL,
 282                            &maintenance_set_cmdlist,
 283                            &maintenance_show_cmdlist);
 284 }
 285
 286 /* There are only two global functions left.  */
 287
 288 void
 289 x86_use_watchpoints (struct target_ops *t)
 290 {
 291   /* After a watchpoint trap, the PC points to the instruction after the
 292      one that caused the trap.  Therefore we don't need to step over it.
 293      But we do need to reset the status register to avoid another trap.  */
 294   t->to_have_continuable_watchpoint = 1;
 295
 296   t->to_can_use_hw_breakpoint = x86_can_use_hw_breakpoint;
 297   t->to_region_ok_for_hw_watchpoint = x86_region_ok_for_watchpoint;
 298   t->to_stopped_by_watchpoint = x86_stopped_by_watchpoint;
 299   t->to_stopped_data_address = x86_stopped_data_address;
 300   t->to_insert_watchpoint = x86_insert_watchpoint;
 301   t->to_remove_watchpoint = x86_remove_watchpoint;
 302   t->to_insert_hw_breakpoint = x86_insert_hw_breakpoint;
 303   t->to_remove_hw_breakpoint = x86_remove_hw_breakpoint;
 304 }
 305
 306 void
 307 x86_set_debug_register_length (int len)
 308 {
 309   /* This function should be called only once for each native target.  */
 310   gdb_assert (x86_dr_low.debug_register_length == 0);
 311   gdb_assert (len == 4 || len == 8);
 312   x86_dr_low.debug_register_length = len;
 313   add_show_debug_regs_command ();
 314 }