1 /* Native-dependent code for x86 (i386 and x86-64). 2 3 Copyright (C) 2001-2023 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 /* See x86-nat.h. */ 50 51 struct x86_debug_reg_state * 52 x86_lookup_debug_reg_state (pid_t pid) 53 { 54 auto it = x86_debug_process_state.find (pid); 55 if (it != x86_debug_process_state.end ()) 56 return &it->second; 57 58 return nullptr; 59 } 60 61 /* Get debug registers state for process PID. */ 62 63 struct x86_debug_reg_state * 64 x86_debug_reg_state (pid_t pid) 65 { 66 return &x86_debug_process_state[pid]; 67 } 68 69 /* See declaration in x86-nat.h. */ 70 71 void 72 x86_forget_process (pid_t pid) 73 { 74 x86_debug_process_state.erase (pid); 75 } 76 77 /* Clear the reference counts and forget everything we knew about the 78 debug registers. */ 79 80 void 81 x86_cleanup_dregs (void) 82 { 83 /* Starting from scratch has the same effect. */ 84 x86_forget_process (inferior_ptid.pid ()); 85 } 86 87 /* Insert a watchpoint to watch a memory region which starts at 88 address ADDR and whose length is LEN bytes. Watch memory accesses 89 of the type TYPE. Return 0 on success, -1 on failure. */ 90 91 int 92 x86_insert_watchpoint (CORE_ADDR addr, int len, 93 enum target_hw_bp_type type, struct expression *cond) 94 { 95 struct x86_debug_reg_state *state 96 = x86_debug_reg_state (inferior_ptid.pid ()); 97 98 return x86_dr_insert_watchpoint (state, type, addr, len); 99 } 100 101 /* Remove a watchpoint that watched the memory region which starts at 102 address ADDR, whose length is LEN bytes, and for accesses of the 103 type TYPE. Return 0 on success, -1 on failure. */ 104 int 105 x86_remove_watchpoint (CORE_ADDR addr, int len, 106 enum target_hw_bp_type type, struct expression *cond) 107 { 108 struct x86_debug_reg_state *state 109 = x86_debug_reg_state (inferior_ptid.pid ()); 110 111 return x86_dr_remove_watchpoint (state, type, addr, len); 112 } 113 114 /* Return non-zero if we can watch a memory region that starts at 115 address ADDR and whose length is LEN bytes. */ 116 117 int 118 x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len) 119 { 120 struct x86_debug_reg_state *state 121 = x86_debug_reg_state (inferior_ptid.pid ()); 122 123 return x86_dr_region_ok_for_watchpoint (state, addr, len); 124 } 125 126 /* If the inferior has some break/watchpoint that triggered, set the 127 address associated with that break/watchpoint and return non-zero. 128 Otherwise, return zero. */ 129 130 int 131 x86_stopped_data_address (CORE_ADDR *addr_p) 132 { 133 struct x86_debug_reg_state *state 134 = x86_debug_reg_state (inferior_ptid.pid ()); 135 136 return x86_dr_stopped_data_address (state, addr_p); 137 } 138 139 /* Return non-zero if the inferior has some watchpoint that triggered. 140 Otherwise return zero. */ 141 142 int 143 x86_stopped_by_watchpoint () 144 { 145 struct x86_debug_reg_state *state 146 = x86_debug_reg_state (inferior_ptid.pid ()); 147 148 return x86_dr_stopped_by_watchpoint (state); 149 } 150 151 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address. 152 Return 0 on success, EBUSY on failure. */ 153 154 int 155 x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt) 156 { 157 struct x86_debug_reg_state *state 158 = x86_debug_reg_state (inferior_ptid.pid ()); 159 160 bp_tgt->placed_address = bp_tgt->reqstd_address; 161 return x86_dr_insert_watchpoint (state, hw_execute, 162 bp_tgt->placed_address, 1) ? EBUSY : 0; 163 } 164 165 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address. 166 Return 0 on success, -1 on failure. */ 167 168 int 169 x86_remove_hw_breakpoint (struct gdbarch *gdbarch, 170 struct bp_target_info *bp_tgt) 171 { 172 struct x86_debug_reg_state *state 173 = x86_debug_reg_state (inferior_ptid.pid ()); 174 175 return x86_dr_remove_watchpoint (state, hw_execute, 176 bp_tgt->placed_address, 1); 177 } 178 179 /* Returns the number of hardware watchpoints of type TYPE that we can 180 set. Value is positive if we can set CNT watchpoints, zero if 181 setting watchpoints of type TYPE is not supported, and negative if 182 CNT is more than the maximum number of watchpoints of type TYPE 183 that we can support. TYPE is one of bp_hardware_watchpoint, 184 bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint. 185 CNT is the number of such watchpoints used so far (including this 186 one). OTHERTYPE is non-zero if other types of watchpoints are 187 currently enabled. 188 189 We always return 1 here because we don't have enough information 190 about possible overlap of addresses that they want to watch. As an 191 extreme example, consider the case where all the watchpoints watch 192 the same address and the same region length: then we can handle a 193 virtually unlimited number of watchpoints, due to debug register 194 sharing implemented via reference counts in x86-nat.c. */ 195 196 int 197 x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype) 198 { 199 return 1; 200 } 201 202 /* Return non-zero if the inferior has some breakpoint that triggered. 203 Otherwise return zero. */ 204 205 int 206 x86_stopped_by_hw_breakpoint () 207 { 208 struct x86_debug_reg_state *state 209 = x86_debug_reg_state (inferior_ptid.pid ()); 210 211 return x86_dr_stopped_by_hw_breakpoint (state); 212 } 213 214 static void 215 add_show_debug_regs_command (void) 216 { 217 /* A maintenance command to enable printing the internal DRi mirror 218 variables. */ 219 add_setshow_boolean_cmd ("show-debug-regs", class_maintenance, 220 &show_debug_regs, _("\ 221 Set whether to show variables that mirror the x86 debug registers."), _("\ 222 Show whether to show variables that mirror the x86 debug registers."), _("\ 223 Use \"on\" to enable, \"off\" to disable.\n\ 224 If enabled, the debug registers values are shown when GDB inserts\n\ 225 or removes a hardware breakpoint or watchpoint, and when the inferior\n\ 226 triggers a breakpoint or watchpoint."), 227 NULL, 228 NULL, 229 &maintenance_set_cmdlist, 230 &maintenance_show_cmdlist); 231 } 232 233 /* See x86-nat.h. */ 234 235 void 236 x86_set_debug_register_length (int len) 237 { 238 /* This function should be called only once for each native target. */ 239 gdb_assert (x86_dr_low.debug_register_length == 0); 240 gdb_assert (len == 4 || len == 8); 241 x86_dr_low.debug_register_length = len; 242 add_show_debug_regs_command (); 243 } 244