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, CORE_ADDR addr, int len,
 153                        enum target_hw_bp_type type, struct expression *cond)
 154 {
 155   struct x86_debug_reg_state *state
 156     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 157
 158   return x86_dr_insert_watchpoint (state, type, addr, len);
 159 }
 160
 161 /* Remove a watchpoint that watched the memory region which starts at
 162    address ADDR, whose length is LEN bytes, and for accesses of the
 163    type TYPE.  Return 0 on success, -1 on failure.  */
 164 static int
 165 x86_remove_watchpoint (struct target_ops *self, CORE_ADDR addr, int len,
 166                        enum target_hw_bp_type type, struct expression *cond)
 167 {
 168   struct x86_debug_reg_state *state
 169     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 170
 171   return x86_dr_remove_watchpoint (state, type, addr, len);
 172 }
 173
 174 /* Return non-zero if we can watch a memory region that starts at
 175    address ADDR and whose length is LEN bytes.  */
 176
 177 static int
 178 x86_region_ok_for_watchpoint (struct target_ops *self,
 179                               CORE_ADDR addr, int len)
 180 {
 181   struct x86_debug_reg_state *state
 182     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 183
 184   return x86_dr_region_ok_for_watchpoint (state, addr, len);
 185 }
 186
 187 /* If the inferior has some break/watchpoint that triggered, set the
 188    address associated with that break/watchpoint and return non-zero.
 189    Otherwise, return zero.  */
 190
 191 static int
 192 x86_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p)
 193 {
 194   struct x86_debug_reg_state *state
 195     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 196
 197   return x86_dr_stopped_data_address (state, addr_p);
 198 }
 199
 200 /* Return non-zero if the inferior has some watchpoint that triggered.
 201    Otherwise return zero.  */
 202
 203 static int
 204 x86_stopped_by_watchpoint (struct target_ops *ops)
 205 {
 206   struct x86_debug_reg_state *state
 207     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 208
 209   return x86_dr_stopped_by_watchpoint (state);
 210 }
 211
 212 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
 213    Return 0 on success, EBUSY on failure.  */
 214
 215 static int
 216 x86_insert_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 217                           struct bp_target_info *bp_tgt)
 218 {
 219   struct x86_debug_reg_state *state
 220     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 221
 222   bp_tgt->placed_address = bp_tgt->reqstd_address;
 223   return x86_dr_insert_watchpoint (state, hw_execute,
 224                                    bp_tgt->placed_address, 1) ? EBUSY : 0;
 225 }
 226
 227 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
 228    Return 0 on success, -1 on failure.  */
 229
 230 static int
 231 x86_remove_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch,
 232                           struct bp_target_info *bp_tgt)
 233 {
 234   struct x86_debug_reg_state *state
 235     = x86_debug_reg_state (ptid_get_pid (inferior_ptid));
 236
 237   return x86_dr_remove_watchpoint (state, hw_execute,
 238                                    bp_tgt->placed_address, 1);
 239 }
 240
 241 /* Returns the number of hardware watchpoints of type TYPE that we can
 242    set.  Value is positive if we can set CNT watchpoints, zero if
 243    setting watchpoints of type TYPE is not supported, and negative if
 244    CNT is more than the maximum number of watchpoints of type TYPE
 245    that we can support.  TYPE is one of bp_hardware_watchpoint,
 246    bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
 247    CNT is the number of such watchpoints used so far (including this
 248    one).  OTHERTYPE is non-zero if other types of watchpoints are
 249    currently enabled.
 250
 251    We always return 1 here because we don't have enough information
 252    about possible overlap of addresses that they want to watch.  As an
 253    extreme example, consider the case where all the watchpoints watch
 254    the same address and the same region length: then we can handle a
 255    virtually unlimited number of watchpoints, due to debug register
 256    sharing implemented via reference counts in i386-nat.c.  */
 257
 258 static int
 259 x86_can_use_hw_breakpoint (struct target_ops *self,
 260                            enum bptype type, int cnt, int othertype)
 261 {
 262   return 1;
 263 }
 264
 265 static void
 266 add_show_debug_regs_command (void)
 267 {
 268   /* A maintenance command to enable printing the internal DRi mirror
 269      variables.  */
 270   add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
 271                            &show_debug_regs, _("\
 272 Set whether to show variables that mirror the x86 debug registers."), _("\
 273 Show whether to show variables that mirror the x86 debug registers."), _("\
 274 Use \"on\" to enable, \"off\" to disable.\n\
 275 If enabled, the debug registers values are shown when GDB inserts\n\
 276 or removes a hardware breakpoint or watchpoint, and when the inferior\n\
 277 triggers a breakpoint or watchpoint."),
 278                            NULL,
 279                            NULL,
 280                            &maintenance_set_cmdlist,
 281                            &maintenance_show_cmdlist);
 282 }
 283
 284 /* There are only two global functions left.  */
 285
 286 void
 287 x86_use_watchpoints (struct target_ops *t)
 288 {
 289   /* After a watchpoint trap, the PC points to the instruction after the
 290      one that caused the trap.  Therefore we don't need to step over it.
 291      But we do need to reset the status register to avoid another trap.  */
 292   t->to_have_continuable_watchpoint = 1;
 293
 294   t->to_can_use_hw_breakpoint = x86_can_use_hw_breakpoint;
 295   t->to_region_ok_for_hw_watchpoint = x86_region_ok_for_watchpoint;
 296   t->to_stopped_by_watchpoint = x86_stopped_by_watchpoint;
 297   t->to_stopped_data_address = x86_stopped_data_address;
 298   t->to_insert_watchpoint = x86_insert_watchpoint;
 299   t->to_remove_watchpoint = x86_remove_watchpoint;
 300   t->to_insert_hw_breakpoint = x86_insert_hw_breakpoint;
 301   t->to_remove_hw_breakpoint = x86_remove_hw_breakpoint;
 302 }
 303
 304 void
 305 x86_set_debug_register_length (int len)
 306 {
 307   /* This function should be called only once for each native target.  */
 308   gdb_assert (x86_dr_low.debug_register_length == 0);
 309   gdb_assert (len == 4 || len == 8);
 310   x86_dr_low.debug_register_length = len;
 311   add_show_debug_regs_command ();
 312 }