gdb/x86-nat.c - gdb

Global variables defined

Data types defined

Functions defined

Source code

  1. /* Native-dependent code for x86 (i386 and x86-64).

  3.    Copyright (C) 2001-2015 Free Software Foundation, Inc.

  5.    This file is part of GDB.

  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.

  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.

  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/>.  */

  20. #include "defs.h"
  21. #include "x86-nat.h"
  22. #include "gdbcmd.h"
  23. #include "inferior.h"

  25. /* Support for hardware watchpoints and breakpoints using the x86
  26.    debug registers.

  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.

  33.    The functions below implement debug registers sharing by reference
  34.    counts, and allow to watch regions up to 16 bytes long.  */

  36. /* Low-level function vector.  */
  37. ‌struct x86_dr_low_type x86_dr_low;

  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).  */

  44. ‌struct x86_process_info
  45. {
  46.   /* Linked list.  */
  47.   struct x86_process_info *next;

  49.   /* The process identifier.  */
  50.   pid_t pid;

  52.   /* Copy of x86 hardware debug registers.  */
  53.   struct x86_debug_reg_state state;
  54. };

  56. ‌static struct x86_process_info *x86_process_list = NULL;

  58. /* Find process data for process PID.  */

  60. static struct x86_process_info *
  61. ‌x86_find_process_pid (pid_t pid)
  62. {
  63.   struct x86_process_info *proc;

  65.   for (proc = x86_process_list; proc; proc = proc->next)
  66.     if (proc->pid == pid)
  67.       return proc;

  69.   return NULL;
  70. }

  72. /* Add process data for process PID.  Returns newly allocated info
  73.    object.  */

  75. static struct x86_process_info *
  76. ‌x86_add_process (pid_t pid)
  77. {
  78.   struct x86_process_info *proc;

  80.   proc = xcalloc (1, sizeof (*proc));
  81.   proc->pid = pid;

  83.   proc->next = x86_process_list;
  84.   x86_process_list = proc;

  86.   return proc;
  87. }

  89. /* Get data specific info for process PID, creating it if necessary.
  90.    Never returns NULL.  */

  92. static struct x86_process_info *
  93. ‌x86_process_info_get (pid_t pid)
  94. {
  95.   struct x86_process_info *proc;

  97.   proc = x86_find_process_pid (pid);
  98.   if (proc == NULL)
  99.     proc = x86_add_process (pid);

  101.   return proc;
  102. }

  104. /* Get debug registers state for process PID.  */

  106. struct x86_debug_reg_state *
  107. ‌x86_debug_reg_state (pid_t pid)
  108. {
  109.   return &x86_process_info_get (pid)->state;
  110. }

  112. /* See declaration in i386-nat.h.  */

  114. void
  115. ‌x86_forget_process (pid_t pid)
  116. {
  117.   struct x86_process_info *proc, **proc_link;

  119.   proc = x86_process_list;
  120.   proc_link = &x86_process_list;

  122.   while (proc != NULL)
  123.     {
  124.       if (proc->pid == pid)
  125.         {
  126.           *proc_link = proc->next;

  128.           xfree (proc);
  129.           return;
  130.         }

  132.       proc_link = &proc->next;
  133.       proc = *proc_link;
  134.     }
  135. }

  137. /* Clear the reference counts and forget everything we knew about the
  138.    debug registers.  */

  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. }

  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.  */

  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));

  159.   return x86_dr_insert_watchpoint (state, type, addr, len);
  160. }

  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));

  173.   return x86_dr_remove_watchpoint (state, type, addr, len);
  174. }

  176. /* Return non-zero if we can watch a memory region that starts at
  177.    address ADDR and whose length is LEN bytes.  */

  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));

  186.   return x86_dr_region_ok_for_watchpoint (state, addr, len);
  187. }

  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.  */

  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));

  199.   return x86_dr_stopped_data_address (state, addr_p);
  200. }

  202. /* Return non-zero if the inferior has some watchpoint that triggered.
  203.    Otherwise return zero.  */

  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));

  211.   return x86_dr_stopped_by_watchpoint (state);
  212. }

  214. /* Insert a hardware-assisted breakpoint at BP_TGT->reqstd_address.
  215.    Return 0 on success, EBUSY on failure.  */

  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));

  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. }

  229. /* Remove a hardware-assisted breakpoint at BP_TGT->placed_address.
  230.    Return 0 on success, -1 on failure.  */

  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));

  239.   return x86_dr_remove_watchpoint (state, hw_execute,
  240.                                    bp_tgt->placed_address, 1);
  241. }

  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.

  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.  */

  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. }

  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. }

  286. /* There are only two global functions left.  */

  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;

  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. }

  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. }