1 /* Native-dependent code for x86 (i386 and x86-64). 2 3 Copyright (C) 2001-2019 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 = XCNEW (struct x86_process_info); 79 80 proc->pid = pid; 81 proc->next = x86_process_list; 82 x86_process_list = proc; 83 84 return proc; 85 } 86 87 /* Get data specific info for process PID, creating it if necessary. 88 Never returns NULL. */ 89 90 static struct x86_process_info * 91 x86_process_info_get (pid_t pid) 92 { 93 struct x86_process_info *proc; 94 95 proc = x86_find_process_pid (pid); 96 if (proc == NULL) 97 proc = x86_add_process (pid); 98 99 return proc; 100 } 101 102 /* Get debug registers state for process PID. */ 103 104 struct x86_debug_reg_state * 105 x86_debug_reg_state (pid_t pid) 106 { 107 return &x86_process_info_get (pid)->state; 108 } 109 110 /* See declaration in x86-nat.h. */ 111 112 void 113 x86_forget_process (pid_t pid) 114 { 115 struct x86_process_info *proc, **proc_link; 116 117 proc = x86_process_list; 118 proc_link = &x86_process_list; 119 120 while (proc != NULL) 121 { 122 if (proc->pid == pid) 123 { 124 *proc_link = proc->next; 125 126 xfree (proc); 127 return; 128 } 129 130 proc_link = &proc->next; 131 proc = *proc_link; 132 } 133 } 134 135 /* Clear the reference counts and forget everything we knew about the 136 debug registers. */ 137 138 void 139 x86_cleanup_dregs (void) 140 { 141 /* Starting from scratch has the same effect. */ 142 x86_forget_process (inferior_ptid.pid ()); 143 } 144 145 /* Insert a watchpoint to watch a memory region which starts at 146 address ADDR and whose length is LEN bytes. Watch memory accesses 147 of the type TYPE. Return 0 on success, -1 on failure. */ 148 149 int 150 x86_insert_watchpoint (CORE_ADDR addr, int len, 151 enum target_hw_bp_type type, struct expression *cond) 152 { 153 struct x86_debug_reg_state *state 154 = x86_debug_reg_state (inferior_ptid.pid ()); 155 156 return x86_dr_insert_watchpoint (state, type, addr, len); 157 } 158 159 /* Remove a watchpoint that watched the memory region which starts at 160 address ADDR, whose length is LEN bytes, and for accesses of the 161 type TYPE. Return 0 on success, -1 on failure. */ 162 int 163 x86_remove_watchpoint (CORE_ADDR addr, int len, 164 enum target_hw_bp_type type, struct expression *cond) 165 { 166 struct x86_debug_reg_state *state 167 = x86_debug_reg_state (inferior_ptid.pid ()); 168 169 return x86_dr_remove_watchpoint (state, type, addr, len); 170 } 171 172 /* Return non-zero if we can watch a memory region that starts at 173 address ADDR and whose length is LEN bytes. */ 174 175 int 176 x86_region_ok_for_hw_watchpoint (CORE_ADDR addr, int len) 177 { 178 struct x86_debug_reg_state *state 179 = x86_debug_reg_state (inferior_ptid.pid ()); 180 181 return x86_dr_region_ok_for_watchpoint (state, addr, len); 182 } 183 184 /* If the inferior has some break/watchpoint that triggered, set the 185 address associated with that break/watchpoint and return non-zero. 186 Otherwise, return zero. */ 187 188 int 189 x86_stopped_data_address (CORE_ADDR *addr_p) 190 { 191 struct x86_debug_reg_state *state 192 = x86_debug_reg_state (inferior_ptid.pid ()); 193 194 return x86_dr_stopped_data_address (state, addr_p); 195 } 196 197 /* Return non-zero if the inferior has some watchpoint that triggered. 198 Otherwise return zero. */ 199 200 int 201 x86_stopped_by_watchpoint () 202 { 203 struct x86_debug_reg_state *state 204 = x86_debug_reg_state (inferior_ptid.pid ()); 205 206 return x86_dr_stopped_by_watchpoint (state); 207 } 208 209 /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address. 210 Return 0 on success, EBUSY on failure. */ 211 212 int 213 x86_insert_hw_breakpoint (struct gdbarch *gdbarch, struct bp_target_info *bp_tgt) 214 { 215 struct x86_debug_reg_state *state 216 = x86_debug_reg_state (inferior_ptid.pid ()); 217 218 bp_tgt->placed_address = bp_tgt->reqstd_address; 219 return x86_dr_insert_watchpoint (state, hw_execute, 220 bp_tgt->placed_address, 1) ? EBUSY : 0; 221 } 222 223 /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address. 224 Return 0 on success, -1 on failure. */ 225 226 int 227 x86_remove_hw_breakpoint (struct gdbarch *gdbarch, 228 struct bp_target_info *bp_tgt) 229 { 230 struct x86_debug_reg_state *state 231 = x86_debug_reg_state (inferior_ptid.pid ()); 232 233 return x86_dr_remove_watchpoint (state, hw_execute, 234 bp_tgt->placed_address, 1); 235 } 236 237 /* Returns the number of hardware watchpoints of type TYPE that we can 238 set. Value is positive if we can set CNT watchpoints, zero if 239 setting watchpoints of type TYPE is not supported, and negative if 240 CNT is more than the maximum number of watchpoints of type TYPE 241 that we can support. TYPE is one of bp_hardware_watchpoint, 242 bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint. 243 CNT is the number of such watchpoints used so far (including this 244 one). OTHERTYPE is non-zero if other types of watchpoints are 245 currently enabled. 246 247 We always return 1 here because we don't have enough information 248 about possible overlap of addresses that they want to watch. As an 249 extreme example, consider the case where all the watchpoints watch 250 the same address and the same region length: then we can handle a 251 virtually unlimited number of watchpoints, due to debug register 252 sharing implemented via reference counts in x86-nat.c. */ 253 254 int 255 x86_can_use_hw_breakpoint (enum bptype type, int cnt, int othertype) 256 { 257 return 1; 258 } 259 260 /* Return non-zero if the inferior has some breakpoint that triggered. 261 Otherwise return zero. */ 262 263 int 264 x86_stopped_by_hw_breakpoint () 265 { 266 struct x86_debug_reg_state *state 267 = x86_debug_reg_state (inferior_ptid.pid ()); 268 269 return x86_dr_stopped_by_hw_breakpoint (state); 270 } 271 272 static void 273 add_show_debug_regs_command (void) 274 { 275 /* A maintenance command to enable printing the internal DRi mirror 276 variables. */ 277 add_setshow_boolean_cmd ("show-debug-regs", class_maintenance, 278 &show_debug_regs, _("\ 279 Set whether to show variables that mirror the x86 debug registers."), _("\ 280 Show whether to show variables that mirror the x86 debug registers."), _("\ 281 Use \"on\" to enable, \"off\" to disable.\n\ 282 If enabled, the debug registers values are shown when GDB inserts\n\ 283 or removes a hardware breakpoint or watchpoint, and when the inferior\n\ 284 triggers a breakpoint or watchpoint."), 285 NULL, 286 NULL, 287 &maintenance_set_cmdlist, 288 &maintenance_show_cmdlist); 289 } 290 291 /* See x86-nat.h. */ 292 293 void 294 x86_set_debug_register_length (int len) 295 { 296 /* This function should be called only once for each native target. */ 297 gdb_assert (x86_dr_low.debug_register_length == 0); 298 gdb_assert (len == 4 || len == 8); 299 x86_dr_low.debug_register_length = len; 300 add_show_debug_regs_command (); 301 } 302