| 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, |
| 153 | CORE_ADDR addr, int len, int type, |
| 154 | struct expression *cond) |
| 155 | { |
| 156 | struct x86_debug_reg_state *state |
| 157 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 158 | |
| 159 | return x86_dr_insert_watchpoint (state, type, addr, len); |
| 160 | } |
| 161 | |
| 162 | /* Remove a watchpoint that watched the memory region which starts at |
| 163 | address ADDR, whose length is LEN bytes, and for accesses of the |
| 164 | type TYPE. Return 0 on success, -1 on failure. */ |
| 165 | static int |
| 166 | x86_remove_watchpoint (struct target_ops *self, |
| 167 | CORE_ADDR addr, int len, int type, |
| 168 | struct expression *cond) |
| 169 | { |
| 170 | struct x86_debug_reg_state *state |
| 171 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 172 | |
| 173 | return x86_dr_remove_watchpoint (state, type, addr, len); |
| 174 | } |
| 175 | |
| 176 | /* Return non-zero if we can watch a memory region that starts at |
| 177 | address ADDR and whose length is LEN bytes. */ |
| 178 | |
| 179 | static int |
| 180 | x86_region_ok_for_watchpoint (struct target_ops *self, |
| 181 | CORE_ADDR addr, int len) |
| 182 | { |
| 183 | struct x86_debug_reg_state *state |
| 184 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 185 | |
| 186 | return x86_dr_region_ok_for_watchpoint (state, addr, len); |
| 187 | } |
| 188 | |
| 189 | /* If the inferior has some break/watchpoint that triggered, set the |
| 190 | address associated with that break/watchpoint and return non-zero. |
| 191 | Otherwise, return zero. */ |
| 192 | |
| 193 | static int |
| 194 | x86_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p) |
| 195 | { |
| 196 | struct x86_debug_reg_state *state |
| 197 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 198 | |
| 199 | return x86_dr_stopped_data_address (state, addr_p); |
| 200 | } |
| 201 | |
| 202 | /* Return non-zero if the inferior has some watchpoint that triggered. |
| 203 | Otherwise return zero. */ |
| 204 | |
| 205 | static int |
| 206 | x86_stopped_by_watchpoint (struct target_ops *ops) |
| 207 | { |
| 208 | struct x86_debug_reg_state *state |
| 209 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 210 | |
| 211 | return x86_dr_stopped_by_watchpoint (state); |
| 212 | } |
| 213 | |
| 214 | /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address. |
| 215 | Return 0 on success, EBUSY on failure. */ |
| 216 | |
| 217 | static int |
| 218 | x86_insert_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch, |
| 219 | struct bp_target_info *bp_tgt) |
| 220 | { |
| 221 | struct x86_debug_reg_state *state |
| 222 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 223 | |
| 224 | bp_tgt->placed_address = bp_tgt->reqstd_address; |
| 225 | return x86_dr_insert_watchpoint (state, hw_execute, |
| 226 | bp_tgt->placed_address, 1) ? EBUSY : 0; |
| 227 | } |
| 228 | |
| 229 | /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address. |
| 230 | Return 0 on success, -1 on failure. */ |
| 231 | |
| 232 | static int |
| 233 | x86_remove_hw_breakpoint (struct target_ops *self, struct gdbarch *gdbarch, |
| 234 | struct bp_target_info *bp_tgt) |
| 235 | { |
| 236 | struct x86_debug_reg_state *state |
| 237 | = x86_debug_reg_state (ptid_get_pid (inferior_ptid)); |
| 238 | |
| 239 | return x86_dr_remove_watchpoint (state, hw_execute, |
| 240 | bp_tgt->placed_address, 1); |
| 241 | } |
| 242 | |
| 243 | /* Returns the number of hardware watchpoints of type TYPE that we can |
| 244 | set. Value is positive if we can set CNT watchpoints, zero if |
| 245 | setting watchpoints of type TYPE is not supported, and negative if |
| 246 | CNT is more than the maximum number of watchpoints of type TYPE |
| 247 | that we can support. TYPE is one of bp_hardware_watchpoint, |
| 248 | bp_read_watchpoint, bp_write_watchpoint, or bp_hardware_breakpoint. |
| 249 | CNT is the number of such watchpoints used so far (including this |
| 250 | one). OTHERTYPE is non-zero if other types of watchpoints are |
| 251 | currently enabled. |
| 252 | |
| 253 | We always return 1 here because we don't have enough information |
| 254 | about possible overlap of addresses that they want to watch. As an |
| 255 | extreme example, consider the case where all the watchpoints watch |
| 256 | the same address and the same region length: then we can handle a |
| 257 | virtually unlimited number of watchpoints, due to debug register |
| 258 | sharing implemented via reference counts in i386-nat.c. */ |
| 259 | |
| 260 | static int |
| 261 | x86_can_use_hw_breakpoint (struct target_ops *self, |
| 262 | int type, int cnt, int othertype) |
| 263 | { |
| 264 | return 1; |
| 265 | } |
| 266 | |
| 267 | static void |
| 268 | add_show_debug_regs_command (void) |
| 269 | { |
| 270 | /* A maintenance command to enable printing the internal DRi mirror |
| 271 | variables. */ |
| 272 | add_setshow_boolean_cmd ("show-debug-regs", class_maintenance, |
| 273 | &show_debug_regs, _("\ |
| 274 | Set whether to show variables that mirror the x86 debug registers."), _("\ |
| 275 | Show whether to show variables that mirror the x86 debug registers."), _("\ |
| 276 | Use \"on\" to enable, \"off\" to disable.\n\ |
| 277 | If enabled, the debug registers values are shown when GDB inserts\n\ |
| 278 | or removes a hardware breakpoint or watchpoint, and when the inferior\n\ |
| 279 | triggers a breakpoint or watchpoint."), |
| 280 | NULL, |
| 281 | NULL, |
| 282 | &maintenance_set_cmdlist, |
| 283 | &maintenance_show_cmdlist); |
| 284 | } |
| 285 | |
| 286 | /* There are only two global functions left. */ |
| 287 | |
| 288 | void |
| 289 | x86_use_watchpoints (struct target_ops *t) |
| 290 | { |
| 291 | /* After a watchpoint trap, the PC points to the instruction after the |
| 292 | one that caused the trap. Therefore we don't need to step over it. |
| 293 | But we do need to reset the status register to avoid another trap. */ |
| 294 | t->to_have_continuable_watchpoint = 1; |
| 295 | |
| 296 | t->to_can_use_hw_breakpoint = x86_can_use_hw_breakpoint; |
| 297 | t->to_region_ok_for_hw_watchpoint = x86_region_ok_for_watchpoint; |
| 298 | t->to_stopped_by_watchpoint = x86_stopped_by_watchpoint; |
| 299 | t->to_stopped_data_address = x86_stopped_data_address; |
| 300 | t->to_insert_watchpoint = x86_insert_watchpoint; |
| 301 | t->to_remove_watchpoint = x86_remove_watchpoint; |
| 302 | t->to_insert_hw_breakpoint = x86_insert_hw_breakpoint; |
| 303 | t->to_remove_hw_breakpoint = x86_remove_hw_breakpoint; |
| 304 | } |
| 305 | |
| 306 | void |
| 307 | x86_set_debug_register_length (int len) |
| 308 | { |
| 309 | /* This function should be called only once for each native target. */ |
| 310 | gdb_assert (x86_dr_low.debug_register_length == 0); |
| 311 | gdb_assert (len == 4 || len == 8); |
| 312 | x86_dr_low.debug_register_length = len; |
| 313 | add_show_debug_regs_command (); |
| 314 | } |