gdb/x86-nat.c

   1 /* Native-dependent code for x86 (i386 and x86-64).
   2
   3    Copyright (C) 2001-2024 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 "x86-nat.h"
  21 #include "cli/cli-cmds.h"
  22 #include "inferior.h"
  23
  24 #include <unordered_map>
  25
  26 /* Support for hardware watchpoints and breakpoints using the x86
  27    debug registers.
  28
  29    This provides several functions for inserting and removing
  30    hardware-assisted breakpoints and watchpoints, testing if one or
  31    more of the watchpoints triggered and at what address, checking
  32    whether a given region can be watched, etc.
  33
  34    The functions below implement debug registers sharing by reference
  35    counts, and allow to watch regions up to 16 bytes long.  */
  36
  37 /* Low-level function vector.  */
  38 struct x86_dr_low_type x86_dr_low;
  39
  40 /* Hash table storing per-process data.  We don't bind this to a
  41    per-inferior registry because of targets like x86 GNU/Linux that
  42    need to keep track of processes that aren't bound to any inferior
  43    (e.g., fork children, checkpoints).  */
  44
  45 static std::unordered_map<pid_t,
  46                           struct x86_debug_reg_state> x86_debug_process_state;
  47
  48 /* See x86-nat.h.  */
  49
  50 struct x86_debug_reg_state *
  51 x86_lookup_debug_reg_state (pid_t pid)
  52 {
  53   auto it = x86_debug_process_state.find (pid);
  54   if (it != x86_debug_process_state.end ())
  55     return &it->second;
  56
  57   return nullptr;
  58 }
  59
  60 /* Get debug registers state for process PID.  */
  61
  62 struct x86_debug_reg_state *
  63 x86_debug_reg_state (pid_t pid)
  64 {
  65   return &x86_debug_process_state[pid];
  66 }
  67
  68 /* See declaration in x86-nat.h.  */
  69
  70 void
  71 x86_forget_process (pid_t pid)
  72 {
  73   x86_debug_process_state.erase (pid);
  74 }
  75
  76 /* Clear the reference counts and forget everything we knew about the
  77    debug registers.  */
  78
  79 void
  80 x86_cleanup_dregs (void)
  81 {
  82   /* Starting from scratch has the same effect.  */
  83   x86_forget_process (inferior_ptid.pid ());
  84 }
  85
  86 /* Insert a watchpoint to watch a memory region which starts at
  87    address ADDR and whose length is LEN bytes.  Watch memory accesses
  88    of the type TYPE.  Return 0 on success, -1 on failure.  */
  89
  90 int
  91 x86_insert_watchpoint (CORE_ADDR addr, int len,
  92                        enum target_hw_bp_type type, struct expression *cond)
  93 {
  94   struct x86_debug_reg_state *state
  95     = x86_debug_reg_state (inferior_ptid.pid ());
  96
  97   return x86_dr_insert_watchpoint (state, type, addr, len);
  98 }
  99
 100 /* Remove a watchpoint that watched the memory region which starts at
 101    address ADDR, whose length is LEN bytes, and for accesses of the
 102    type TYPE.  Return 0 on success, -1 on failure.  */
 103 int
 104 x86_remove_watchpoint (CORE_ADDR addr, int len,
 105                        enum target_hw_bp_type type, struct expression *cond)
 106 {
 107   struct x86_debug_reg_state *state
 108     = x86_debug_reg_state (inferior_ptid.pid ());
 109
 110   return x86_dr_remove_watchpoint (state, type, addr, len);
 111 }
 112
 113 /* Return non-zero if we can watch a memory region that starts at
 114    address ADDR and whose length is LEN bytes.  */
 115
 116 int
 117 x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len)
 118 {
 119   struct x86_debug_reg_state *state
 120     = x86_debug_reg_state (inferior_ptid.pid ());
 121
 122   return x86_dr_region_ok_for_watchpoint (state, addr, len);
 123 }
 124
 125 /* If the inferior has some break/watchpoint that triggered, set the
 126    address associated with that break/watchpoint and return non-zero.
 127    Otherwise, return zero.  */
 128
 129 int
 130 x86_stopped_data_address (CORE_ADDR *addr_p)
 131 {
 132   struct x86_debug_reg_state *state
 133     = x86_debug_reg_state (inferior_ptid.pid ());
 134
 135   return x86_dr_stopped_data_address (state, addr_p);
 136 }
 137
 138 /* Return non-zero if the inferior has some watchpoint that triggered.
 139    Otherwise return zero.  */
 140
 141 int
 142 x86_stopped_by_watchpoint ()
 143 {
 144   struct x86_debug_reg_state *state
 145     = x86_debug_reg_state (inferior_ptid.pid ());
 146
 147   return x86_dr_stopped_by_watchpoint (state);
 148 }
 149
 150 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
 151    Return 0 on success, EBUSY on failure.  */
 152
 153 int
 154 x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt)
 155 {
 156   struct x86_debug_reg_state *state
 157     = x86_debug_reg_state (inferior_ptid.pid ());
 158
 159   bp_tgt->placed_address = bp_tgt->reqstd_address;
 160   return x86_dr_insert_watchpoint (state, hw_execute,
 161                                    bp_tgt->placed_address, 1) ? EBUSY : 0;
 162 }
 163
 164 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
 165    Return 0 on success, -1 on failure.  */
 166
 167 int
 168 x86_remove_hw_breakpoint (struct gdbarch *gdbarch,
 169                           struct bp_target_info *bp_tgt)
 170 {
 171   struct x86_debug_reg_state *state
 172     = x86_debug_reg_state (inferior_ptid.pid ());
 173
 174   return x86_dr_remove_watchpoint (state, hw_execute,
 175                                    bp_tgt->placed_address, 1);
 176 }
 177
 178 /* Returns the number of hardware watchpoints of type TYPE that we can
 179    set.  Value is positive if we can set CNT watchpoints, zero if
 180    setting watchpoints of type TYPE is not supported, and negative if
 181    CNT is more than the maximum number of watchpoints of type TYPE
 182    that we can support.  TYPE is one of bp_hardware_watchpoint,
 183    bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint.
 184    CNT is the number of such watchpoints used so far (including this
 185    one).  OTHERTYPE is non-zero if other types of watchpoints are
 186    currently enabled.
 187
 188    We always return 1 here because we don't have enough information
 189    about possible overlap of addresses that they want to watch.  As an
 190    extreme example, consider the case where all the watchpoints watch
 191    the same address and the same region length: then we can handle a
 192    virtually unlimited number of watchpoints, due to debug register
 193    sharing implemented via reference counts in x86-nat.c.  */
 194
 195 int
 196 x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype)
 197 {
 198   return 1;
 199 }
 200
 201 /* Return non-zero if the inferior has some breakpoint that triggered.
 202    Otherwise return zero.  */
 203
 204 int
 205 x86_stopped_by_hw_breakpoint ()
 206 {
 207   struct x86_debug_reg_state *state
 208     = x86_debug_reg_state (inferior_ptid.pid ());
 209
 210   return x86_dr_stopped_by_hw_breakpoint (state);
 211 }
 212
 213 static void
 214 add_show_debug_regs_command (void)
 215 {
 216   /* A maintenance command to enable printing the internal DRi mirror
 217      variables.  */
 218   add_setshow_boolean_cmd ("show-debug-regs", class_maintenance,
 219                            &show_debug_regs, _("\
 220 Set whether to show variables that mirror the x86 debug registers."), _("\
 221 Show whether to show variables that mirror the x86 debug registers."), _("\
 222 Use \"on\" to enable, \"off\" to disable.\n\
 223 If enabled, the debug registers values are shown when GDB inserts\n\
 224 or removes a hardware breakpoint or watchpoint, and when the inferior\n\
 225 triggers a breakpoint or watchpoint."),
 226                            NULL,
 227                            NULL,
 228                            &maintenance_set_cmdlist,
 229                            &maintenance_show_cmdlist);
 230 }
 231
 232 /* See x86-nat.h.  */
 233
 234 void
 235 x86_set_debug_register_length (int len)
 236 {
 237   /* This function should be called only once for each native target.  */
 238   gdb_assert (x86_dr_low.debug_register_length == 0);
 239   gdb_assert (len == 4 || len == 8);
 240   x86_dr_low.debug_register_length = len;
 241   add_show_debug_regs_command ();
 242 }