gdb/x86-nat.c

   1 /* Native-dependent code for x86 (i386 and x86-64).
   2
   3    Copyright (C) 2001-2022 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 #include <unordered_map>
  26
  27 /* Support for hardware watchpoints and breakpoints using the x86
  28    debug registers.
  29
  30    This provides several functions for inserting and removing
  31    hardware-assisted breakpoints and watchpoints, testing if one or
  32    more of the watchpoints triggered and at what address, checking
  33    whether a given region can be watched, etc.
  34
  35    The functions below implement debug registers sharing by reference
  36    counts, and allow to watch regions up to 16 bytes long.  */
  37
  38 /* Low-level function vector.  */
  39 struct x86_dr_low_type x86_dr_low;
  40
  41 /* Hash table storing per-process data.  We don't bind this to a
  42    per-inferior registry because of targets like x86 GNU/Linux that
  43    need to keep track of processes that aren't bound to any inferior
  44    (e.g., fork children, checkpoints).  */
  45
  46 static std::unordered_map<pid_t,
  47                           struct x86_debug_reg_state> x86_debug_process_state;
  48
  49 /* Get debug registers state for process PID.  */
  50
  51 struct x86_debug_reg_state *
  52 x86_debug_reg_state (pid_t pid)
  53 {
  54   return &x86_debug_process_state[pid];
  55 }
  56
  57 /* See declaration in x86-nat.h.  */
  58
  59 void
  60 x86_forget_process (pid_t pid)
  61 {
  62   x86_debug_process_state.erase (pid);
  63 }
  64
  65 /* Clear the reference counts and forget everything we knew about the
  66    debug registers.  */
  67
  68 void
  69 x86_cleanup_dregs (void)
  70 {
  71   /* Starting from scratch has the same effect.  */
  72   x86_forget_process (inferior_ptid.pid ());
  73 }
  74
  75 /* Insert a watchpoint to watch a memory region which starts at
  76    address ADDR and whose length is LEN bytes.  Watch memory accesses
  77    of the type TYPE.  Return 0 on success, -1 on failure.  */
  78
  79 int
  80 x86_insert_watchpoint (CORE_ADDR addr, int len,
  81                        enum target_hw_bp_type type, struct expression *cond)
  82 {
  83   struct x86_debug_reg_state *state
  84     = x86_debug_reg_state (inferior_ptid.pid ());
  85
  86   return x86_dr_insert_watchpoint (state, type, addr, len);
  87 }
  88
  89 /* Remove a watchpoint that watched the memory region which starts at
  90    address ADDR, whose length is LEN bytes, and for accesses of the
  91    type TYPE.  Return 0 on success, -1 on failure.  */
  92 int
  93 x86_remove_watchpoint (CORE_ADDR addr, int len,
  94                        enum target_hw_bp_type type, struct expression *cond)
  95 {
  96   struct x86_debug_reg_state *state
  97     = x86_debug_reg_state (inferior_ptid.pid ());
  98
  99   return x86_dr_remove_watchpoint (state, type, addr, len);
 100 }
 101
 102 /* Return non-zero if we can watch a memory region that starts at
 103    address ADDR and whose length is LEN bytes.  */
 104
 105 int
 106 x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
 107 {
 108   struct x86_debug_reg_state *state
 109     = x86_debug_reg_state (inferior_ptid.pid ());
 110
 111   return x86_dr_region_ok_for_watchpoint (state, addr, len);
 112 }
 113
 114 /* If the inferior has some break/watchpoint that triggered, set the
 115    address associated with that break/watchpoint and return non-zero.
 116    Otherwise, return zero.  */
 117
 118 int
 119 x86_stopped_data_address (CORE_ADDR *addr_p)
 120 {
 121   struct x86_debug_reg_state *state
 122     = x86_debug_reg_state (inferior_ptid.pid ());
 123
 124   return x86_dr_stopped_data_address (state, addr_p);
 125 }
 126
 127 /* Return non-zero if the inferior has some watchpoint that triggered.
 128    Otherwise return zero.  */
 129
 130 int
 131 x86_stopped_by_watchpoint ()
 132 {
 133   struct x86_debug_reg_state *state
 134     = x86_debug_reg_state (inferior_ptid.pid ());
 135
 136   return x86_dr_stopped_by_watchpoint (state);
 137 }
 138
 139 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
 140    Return 0 on success, EBUSY on failure.  */
 141
 142 int
 143 x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt)
 144 {
 145   struct x86_debug_reg_state *state
 146     = x86_debug_reg_state (inferior_ptid.pid ());
 147
 148   bp_tgt->placed_address = bp_tgt->reqstd_address;
 149   return x86_dr_insert_watchpoint (state, hw_execute,
 150                                    bp_tgt->placed_address, 1) ? EBUSY : 0;
 151 }
 152
 153 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
 154    Return 0 on success, -1 on failure.  */
 155
 156 int
 157 x86_remove_hw_breakpoint (struct gdbarch *gdbarch,
 158                           struct bp_target_info *bp_tgt)
 159 {
 160   struct x86_debug_reg_state *state
 161     = x86_debug_reg_state (inferior_ptid.pid ());
 162
 163   return x86_dr_remove_watchpoint (state, hw_execute,
 164                                    bp_tgt->placed_address, 1);
 165 }
 166
 167 /* Returns the number of hardware watchpoints of type TYPE that we can
 168    set.  Value is positive if we can set CNT watchpoints, zero if
 169    setting watchpoints of type TYPE is not supported, and negative if
 170    CNT is more than the maximum number of watchpoints of type TYPE
 171    that we can support.  TYPE is one of bp_hardware_watchpoint,
 172    bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
 173    CNT is the number of such watchpoints used so far (including this
 174    one).  OTHERTYPE is non-zero if other types of watchpoints are
 175    currently enabled.
 176
 177    We always return 1 here because we don't have enough information
 178    about possible overlap of addresses that they want to watch.  As an
 179    extreme example, consider the case where all the watchpoints watch
 180    the same address and the same region length: then we can handle a
 181    virtually unlimited number of watchpoints, due to debug register
 182    sharing implemented via reference counts in x86-nat.c.  */
 183
 184 int
 185 x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype)
 186 {
 187   return 1;
 188 }
 189
 190 /* Return non-zero if the inferior has some breakpoint that triggered.
 191    Otherwise return zero.  */
 192
 193 int
 194 x86_stopped_by_hw_breakpoint ()
 195 {
 196   struct x86_debug_reg_state *state
 197     = x86_debug_reg_state (inferior_ptid.pid ());
 198
 199   return x86_dr_stopped_by_hw_breakpoint (state);
 200 }
 201
 202 static void
 203 add_show_debug_regs_command (void)
 204 {
 205   /* A maintenance command to enable printing the internal DRi mirror
 206      variables.  */
 207   add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
 208                            &show_debug_regs, _("\
 209 Set whether to show variables that mirror the x86 debug registers."), _("\
 210 Show whether to show variables that mirror the x86 debug registers."), _("\
 211 Use \"on\" to enable, \"off\" to disable.\n\
 212 If enabled, the debug registers values are shown when GDB inserts\n\
 213 or removes a hardware breakpoint or watchpoint, and when the inferior\n\
 214 triggers a breakpoint or watchpoint."),
 215                            NULL,
 216                            NULL,
 217                            &maintenance_set_cmdlist,
 218                            &maintenance_show_cmdlist);
 219 }
 220
 221 /* See x86-nat.h.  */
 222
 223 void
 224 x86_set_debug_register_length (int len)
 225 {
 226   /* This function should be called only once for each native target.  */
 227   gdb_assert (x86_dr_low.debug_register_length == 0);
 228   gdb_assert (len == 4 || len == 8);
 229   x86_dr_low.debug_register_length = len;
 230   add_show_debug_regs_command ();
 231 }