* record.c (_initialize_record): Reformat and clarify doc strings

[thirdparty/binutils-gdb.git] / gdb / record.c

/* Process record and replay target for GDB, the GNU debugger.

   Copyright (C) 2008, 2009 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "gdbcmd.h"
#include "regcache.h"
#include "gdbthread.h"
#include "event-top.h"
#include "exceptions.h"
#include "record.h"

#include <signal.h>

#define DEFAULT_RECORD_INSN_MAX_NUM     200000

#define RECORD_IS_REPLAY \
     (record_list->next || execution_direction == EXEC_REVERSE)

/* These are the core struct of record function.

   An record_entry is a record of the value change of a register
   ("record_reg") or a part of memory ("record_mem").  And each
   instruction must has a struct record_entry ("record_end") that points out this
   is the last struct record_entry of this instruction.

   Each struct record_entry is linked to "record_list" by "prev" and "next". */

struct record_reg_entry
{
  int num;
  gdb_byte *val;
};

struct record_mem_entry
{
  CORE_ADDR addr;
  int len;
  gdb_byte *val;
};

enum record_type
{
  record_end = 0,
  record_reg,
  record_mem
};

struct record_entry
{
  struct record_entry *prev;
  struct record_entry *next;
  enum record_type type;
  union
  {
    /* reg */
    struct record_reg_entry reg;
    /* mem */
    struct record_mem_entry mem;
  } u;
};

/* This is the debug switch for process record.  */
int record_debug = 0;

/* These list is for execution log.  */
static struct record_entry record_first;
static struct record_entry *record_list = &record_first;
static struct record_entry *record_arch_list_head = NULL;
static struct record_entry *record_arch_list_tail = NULL;

/* 1 ask user. 0 auto delete the last struct record_entry.  */
static int record_stop_at_limit = 1;
static int record_insn_max_num = DEFAULT_RECORD_INSN_MAX_NUM;
static int record_insn_num = 0;

/* The target_ops of process record.  */
static struct target_ops record_ops;

/* The beneath function pointers.  */
static struct target_ops *record_beneath_to_resume_ops;
static void (*record_beneath_to_resume) (struct target_ops *, ptid_t, int,
                                         enum target_signal);
static struct target_ops *record_beneath_to_wait_ops;
static ptid_t (*record_beneath_to_wait) (struct target_ops *, ptid_t,
                                         struct target_waitstatus *);
static struct target_ops *record_beneath_to_store_registers_ops;
static void (*record_beneath_to_store_registers) (struct target_ops *,
                                                  struct regcache *,
                                                  int regno);
static struct target_ops *record_beneath_to_xfer_partial_ops;
static LONGEST (*record_beneath_to_xfer_partial) (struct target_ops *ops,
                                                  enum target_object object,
                                                  const char *annex,
                                                  gdb_byte *readbuf,
                                                  const gdb_byte *writebuf,
                                                  ULONGEST offset,
                                                  LONGEST len);
static int (*record_beneath_to_insert_breakpoint) (struct bp_target_info *);
static int (*record_beneath_to_remove_breakpoint) (struct bp_target_info *);

static void
record_list_release (struct record_entry *rec)
{
  struct record_entry *tmp;

  if (!rec)
    return;

  while (rec->next)
    {
      rec = rec->next;
    }

  while (rec->prev)
    {
      tmp = rec;
      rec = rec->prev;
      if (tmp->type == record_reg)
        xfree (tmp->u.reg.val);
      else if (tmp->type == record_mem)
        xfree (tmp->u.mem.val);
      xfree (tmp);
    }

  if (rec != &record_first)
    xfree (rec);
}

static void
record_list_release_next (void)
{
  struct record_entry *rec = record_list;
  struct record_entry *tmp = rec->next;
  rec->next = NULL;
  while (tmp)
    {
      rec = tmp->next;
      if (tmp->type == record_reg)
        record_insn_num--;
      else if (tmp->type == record_reg)
        xfree (tmp->u.reg.val);
      else if (tmp->type == record_mem)
        xfree (tmp->u.mem.val);
      xfree (tmp);
      tmp = rec;
    }
}

static void
record_list_release_first (void)
{
  struct record_entry *tmp = NULL;
  enum record_type type;

  if (!record_first.next)
    return;

  while (1)
    {
      type = record_first.next->type;

      if (type == record_reg)
        xfree (record_first.next->u.reg.val);
      else if (type == record_mem)
        xfree (record_first.next->u.mem.val);
      tmp = record_first.next;
      record_first.next = tmp->next;
      xfree (tmp);

      if (!record_first.next)
        {
          gdb_assert (record_insn_num == 1);
          break;
        }

      record_first.next->prev = &record_first;

      if (type == record_end)
        break;
    }

  record_insn_num--;
}

/* Add a struct record_entry to record_arch_list.  */

static void
record_arch_list_add (struct record_entry *rec)
{
  if (record_debug > 1)
    fprintf_unfiltered (gdb_stdlog,
                        "Process record: record_arch_list_add %s.\n",
                        host_address_to_string (rec));

  if (record_arch_list_tail)
    {
      record_arch_list_tail->next = rec;
      rec->prev = record_arch_list_tail;
      record_arch_list_tail = rec;
    }
  else
    {
      record_arch_list_head = rec;
      record_arch_list_tail = rec;
    }
}

/* Record the value of a register NUM to record_arch_list.  */

int
record_arch_list_add_reg (struct regcache *regcache, int num)
{
  struct record_entry *rec;

  if (record_debug > 1)
    fprintf_unfiltered (gdb_stdlog,
                        "Process record: add register num = %d to "
                        "record list.\n",
                        num);

  rec = (struct record_entry *) xmalloc (sizeof (struct record_entry));
  rec->u.reg.val = (gdb_byte *) xmalloc (MAX_REGISTER_SIZE);
  rec->prev = NULL;
  rec->next = NULL;
  rec->type = record_reg;
  rec->u.reg.num = num;

  regcache_raw_read (regcache, num, rec->u.reg.val);

  record_arch_list_add (rec);

  return 0;
}

/* Record the value of a region of memory whose address is ADDR and
   length is LEN to record_arch_list.  */

int
record_arch_list_add_mem (CORE_ADDR addr, int len)
{
  struct record_entry *rec;

  if (record_debug > 1)
    fprintf_unfiltered (gdb_stdlog,
                        "Process record: add mem addr = 0x%s len = %d to "
                        "record list.\n",
                        paddr_nz (addr), len);

  if (!addr)
    return 0;

  rec = (struct record_entry *) xmalloc (sizeof (struct record_entry));
  rec->u.mem.val = (gdb_byte *) xmalloc (len);
  rec->prev = NULL;
  rec->next = NULL;
  rec->type = record_mem;
  rec->u.mem.addr = addr;
  rec->u.mem.len = len;

  if (target_read_memory (addr, rec->u.mem.val, len))
    {
      if (record_debug)
        fprintf_unfiltered (gdb_stdlog,
                            "Process record: error reading memory at "
                            "addr = 0x%s len = %d.\n",
                            paddr_nz (addr), len);
      xfree (rec->u.mem.val);
      xfree (rec);
      return -1;
    }

  record_arch_list_add (rec);

  return 0;
}

/* Add a record_end type struct record_entry to record_arch_list.  */

int
record_arch_list_add_end (void)
{
  struct record_entry *rec;

  if (record_debug > 1)
    fprintf_unfiltered (gdb_stdlog,
                        "Process record: add end to arch list.\n");

  rec = (struct record_entry *) xmalloc (sizeof (struct record_entry));
  rec->prev = NULL;
  rec->next = NULL;
  rec->type = record_end;

  record_arch_list_add (rec);

  return 0;
}

static void
record_check_insn_num (int set_terminal)
{
  if (record_insn_max_num)
    {
      gdb_assert (record_insn_num <= record_insn_max_num);
      if (record_insn_num == record_insn_max_num)
        {
          /* Ask user what to do.  */
          if (record_stop_at_limit)
            {
              int q;
              if (set_terminal)
                target_terminal_ours ();
              q = yquery (_("Do you want to auto delete previous execution "
                            "log entries when record/replay buffer becomes "
                            "full (record stop-at-limit)?"));
              if (set_terminal)
                target_terminal_inferior ();
              if (q)
                record_stop_at_limit = 0;
              else
                error (_("Process record: inferior program stopped."));
            }
        }
    }
}

/* Before inferior step (when GDB record the running message, inferior
   only can step), GDB will call this function to record the values to
   record_list.  This function will call gdbarch_process_record to
   record the running message of inferior and set them to
   record_arch_list, and add it to record_list.  */

static void
record_message_cleanups (void *ignore)
{
  record_list_release (record_arch_list_tail);
}

static int
record_message (void *args)
{
  int ret;
  struct regcache *regcache = args;
  struct cleanup *old_cleanups = make_cleanup (record_message_cleanups, 0);

  record_arch_list_head = NULL;
  record_arch_list_tail = NULL;

  /* Check record_insn_num.  */
  record_check_insn_num (1);

  ret = gdbarch_process_record (get_regcache_arch (regcache),
                                regcache,
                                regcache_read_pc (regcache));
  if (ret > 0)
    error (_("Process record: inferior program stopped."));
  if (ret < 0)
    error (_("Process record: failed to record execution log."));

  discard_cleanups (old_cleanups);

  record_list->next = record_arch_list_head;
  record_arch_list_head->prev = record_list;
  record_list = record_arch_list_tail;

  if (record_insn_num == record_insn_max_num && record_insn_max_num)
    record_list_release_first ();
  else
    record_insn_num++;

  return 1;
}

static int
do_record_message (struct regcache *regcache)
{
  return catch_errors (record_message, regcache, NULL, RETURN_MASK_ALL);
}

/* Set to 1 if record_store_registers and record_xfer_partial
   doesn't need record.  */

static int record_gdb_operation_disable = 0;

struct cleanup *
record_gdb_operation_disable_set (void)
{
  struct cleanup *old_cleanups = NULL;

  old_cleanups =
    make_cleanup_restore_integer (&record_gdb_operation_disable);
  record_gdb_operation_disable = 1;

  return old_cleanups;
}

static void
record_open (char *name, int from_tty)
{
  struct target_ops *t;

  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: record_open\n");

  /* check exec */
  if (!target_has_execution)
    error (_("Process record: the program is not being run."));
  if (non_stop)
    error (_("Process record target can't debug inferior in non-stop mode "
             "(non-stop)."));
  if (target_async_permitted)
    error (_("Process record target can't debug inferior in asynchronous "
             "mode (target-async)."));

  if (!gdbarch_process_record_p (current_gdbarch))
    error (_("Process record: the current architecture doesn't support "
             "record function."));

  /* Check if record target is already running.  */
  if (current_target.to_stratum == record_stratum)
    {
      if (!nquery
          (_("Process record target already running, do you want to delete "
             "the old record log?")))
        return;
    }

  /*Reset the beneath function pointers.  */
  record_beneath_to_resume = NULL;
  record_beneath_to_wait = NULL;
  record_beneath_to_store_registers = NULL;
  record_beneath_to_xfer_partial = NULL;
  record_beneath_to_insert_breakpoint = NULL;
  record_beneath_to_remove_breakpoint = NULL;

  /* Set the beneath function pointers.  */
  for (t = current_target.beneath; t != NULL; t = t->beneath)
    {
      if (!record_beneath_to_resume)
        {
          record_beneath_to_resume = t->to_resume;
          record_beneath_to_resume_ops = t;
        }
      if (!record_beneath_to_wait)
        {
          record_beneath_to_wait = t->to_wait;
          record_beneath_to_wait_ops = t;
        }
      if (!record_beneath_to_store_registers)
        {
          record_beneath_to_store_registers = t->to_store_registers;
          record_beneath_to_store_registers_ops = t;
        }
      if (!record_beneath_to_xfer_partial)
        {
          record_beneath_to_xfer_partial = t->to_xfer_partial;
          record_beneath_to_xfer_partial_ops = t;
        }
      if (!record_beneath_to_insert_breakpoint)
        record_beneath_to_insert_breakpoint = t->to_insert_breakpoint;
      if (!record_beneath_to_remove_breakpoint)
        record_beneath_to_remove_breakpoint = t->to_remove_breakpoint;
    }
  if (!record_beneath_to_resume)
    error (_("Process record can't get to_resume."));
  if (!record_beneath_to_wait)
    error (_("Process record can't get to_wait."));
  if (!record_beneath_to_store_registers)
    error (_("Process record can't get to_store_registers."));
  if (!record_beneath_to_xfer_partial)
    error (_("Process record can't get to_xfer_partial."));
  if (!record_beneath_to_insert_breakpoint)
    error (_("Process record can't get to_insert_breakpoint."));
  if (!record_beneath_to_remove_breakpoint)
    error (_("Process record can't get to_remove_breakpoint."));

  push_target (&record_ops);

  /* Reset */
  record_insn_num = 0;
  record_list = &record_first;
  record_list->next = NULL;
}

static void
record_close (int quitting)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: record_close\n");

  record_list_release (record_list);
}

static int record_resume_step = 0;
static enum target_signal record_resume_siggnal;
static int record_resume_error;

static void
record_resume (struct target_ops *ops, ptid_t ptid, int step,
               enum target_signal siggnal)
{
  record_resume_step = step;
  record_resume_siggnal = siggnal;

  if (!RECORD_IS_REPLAY)
    {
      if (do_record_message (get_current_regcache ()))
        {
          record_resume_error = 0;
        }
      else
        {
          record_resume_error = 1;
          return;
        }
      record_beneath_to_resume (record_beneath_to_resume_ops, ptid, 1,
                                siggnal);
    }
}

static int record_get_sig = 0;

static void
record_sig_handler (int signo)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: get a signal\n");

  /* It will break the running inferior in replay mode.  */
  record_resume_step = 1;

  /* It will let record_wait set inferior status to get the signal
     SIGINT.  */
  record_get_sig = 1;
}

static void
record_wait_cleanups (void *ignore)
{
  if (execution_direction == EXEC_REVERSE)
    {
      if (record_list->next)
        record_list = record_list->next;
    }
  else
    record_list = record_list->prev;
}

/* In replay mode, this function examines the recorded log and
   determines where to stop.  */

static ptid_t
record_wait (struct target_ops *ops,
              ptid_t ptid, struct target_waitstatus *status)
{
  struct cleanup *set_cleanups = record_gdb_operation_disable_set ();

  if (record_debug)
    fprintf_unfiltered (gdb_stdlog,
                        "Process record: record_wait "
                        "record_resume_step = %d\n",
                        record_resume_step);

  if (!RECORD_IS_REPLAY)
    {
      if (record_resume_error)
        {
          /* If record_resume get error, return directly.  */
          status->kind = TARGET_WAITKIND_STOPPED;
          status->value.sig = TARGET_SIGNAL_ABRT;
          return inferior_ptid;
        }

      if (record_resume_step)
        {
          /* This is a single step.  */
          return record_beneath_to_wait (record_beneath_to_wait_ops,
                                                      ptid, status);
        }
      else
        {
          /* This is not a single step.  */
          ptid_t ret;
          CORE_ADDR tmp_pc;

          while (1)
            {
              ret = record_beneath_to_wait (record_beneath_to_wait_ops,
                                            ptid, status);

              if (status->kind == TARGET_WAITKIND_STOPPED
                  && status->value.sig == TARGET_SIGNAL_TRAP)
                {
                  /* Check if there is a breakpoint.  */
                  registers_changed ();
                  tmp_pc = read_pc ();
                  if (breakpoint_inserted_here_p (tmp_pc))
                    {
                      /* There is a breakpoint.  */
                      CORE_ADDR decr_pc_after_break =
                        gdbarch_decr_pc_after_break
                        (get_regcache_arch (get_current_regcache ()));
                      if (decr_pc_after_break)
                        {
                          regcache_write_pc (get_thread_regcache (ret),
                                             tmp_pc + decr_pc_after_break);
                        }
                    }
                  else
                    {
                      /* There is not a breakpoint.  */
                      if (!do_record_message (get_current_regcache ()))
                        {
                          break;
                        }
                      record_beneath_to_resume (record_beneath_to_resume_ops,
                                                ptid, 1,
                                                record_resume_siggnal);
                      continue;
                    }
                }

              /* The inferior is broken by a breakpoint or a signal.  */
              break;
            }

          return ret;
        }
    }
  else
    {
      struct regcache *regcache = get_current_regcache ();
      int continue_flag = 1;
      int first_record_end = 1;
      struct cleanup *old_cleanups = make_cleanup (record_wait_cleanups, 0);
      CORE_ADDR tmp_pc;

      status->kind = TARGET_WAITKIND_STOPPED;

      /* Check breakpoint when forward execute.  */
      if (execution_direction == EXEC_FORWARD)
        {
          tmp_pc = regcache_read_pc (regcache);
          if (breakpoint_inserted_here_p (tmp_pc))
            {
              if (record_debug)
                fprintf_unfiltered (gdb_stdlog,
                                    "Process record: break at 0x%s.\n",
                                    paddr_nz (tmp_pc));
              if (gdbarch_decr_pc_after_break (get_regcache_arch (regcache))
                  && !record_resume_step)
                regcache_write_pc (regcache,
                                   tmp_pc +
                                   gdbarch_decr_pc_after_break
                                   (get_regcache_arch (regcache)));
              goto replay_out;
            }
        }

      record_get_sig = 0;
      signal (SIGINT, record_sig_handler);
      /* If GDB is in terminal_inferior mode, it will not get the signal.
         And in GDB replay mode, GDB doesn't need to be in terminal_inferior
         mode, because inferior will not executed.
         Then set it to terminal_ours to make GDB get the signal.  */
      target_terminal_ours ();

      /* In EXEC_FORWARD mode, record_list points to the tail of prev
         instruction.  */
      if (execution_direction == EXEC_FORWARD && record_list->next)
        record_list = record_list->next;

      /* Loop over the record_list, looking for the next place to
         stop.  */
      do
        {
          /* Check for beginning and end of log.  */
          if (execution_direction == EXEC_REVERSE
              && record_list == &record_first)
            {
              /* Hit beginning of record log in reverse.  */
              status->kind = TARGET_WAITKIND_NO_HISTORY;
              break;
            }
          if (execution_direction != EXEC_REVERSE && !record_list->next)
            {
              /* Hit end of record log going forward.  */
              status->kind = TARGET_WAITKIND_NO_HISTORY;
              break;
            }

          /* Set ptid, register and memory according to record_list.  */
          if (record_list->type == record_reg)
            {
              /* reg */
              gdb_byte reg[MAX_REGISTER_SIZE];
              if (record_debug > 1)
                fprintf_unfiltered (gdb_stdlog,
                                    "Process record: record_reg %s to "
                                    "inferior num = %d.\n",
                                    host_address_to_string (record_list),
                                    record_list->u.reg.num);
              regcache_cooked_read (regcache, record_list->u.reg.num, reg);
              regcache_cooked_write (regcache, record_list->u.reg.num,
                                     record_list->u.reg.val);
              memcpy (record_list->u.reg.val, reg, MAX_REGISTER_SIZE);
            }
          else if (record_list->type == record_mem)
            {
              /* mem */
              gdb_byte *mem = alloca (record_list->u.mem.len);
              if (record_debug > 1)
                fprintf_unfiltered (gdb_stdlog,
                                    "Process record: record_mem %s to "
                                    "inferior addr = 0x%s len = %d.\n",
                                    host_address_to_string (record_list),
                                    paddr_nz (record_list->u.mem.addr),
                                    record_list->u.mem.len);

              if (target_read_memory
                  (record_list->u.mem.addr, mem, record_list->u.mem.len))
                error (_("Process record: error reading memory at "
                         "addr = 0x%s len = %d."),
                       paddr_nz (record_list->u.mem.addr),
                       record_list->u.mem.len);

              if (target_write_memory
                  (record_list->u.mem.addr, record_list->u.mem.val,
                   record_list->u.mem.len))
                error (_
                       ("Process record: error writing memory at "
                        "addr = 0x%s len = %d."),
                       paddr_nz (record_list->u.mem.addr),
                       record_list->u.mem.len);

              memcpy (record_list->u.mem.val, mem, record_list->u.mem.len);
            }
          else
            {
              if (record_debug > 1)
                fprintf_unfiltered (gdb_stdlog,
                                    "Process record: record_end %s to "
                                    "inferior.\n",
                                    host_address_to_string (record_list));

              if (first_record_end && execution_direction == EXEC_REVERSE)
                {
                  /* When reverse excute, the first record_end is the part of
                     current instruction.  */
                  first_record_end = 0;
                }
              else
                {
                  /* In EXEC_REVERSE mode, this is the record_end of prev
                     instruction.
                     In EXEC_FORWARD mode, this is the record_end of current
                     instruction.  */
                  /* step */
                  if (record_resume_step)
                    {
                      if (record_debug > 1)
                        fprintf_unfiltered (gdb_stdlog,
                                            "Process record: step.\n");
                      continue_flag = 0;
                    }

                  /* check breakpoint */
                  tmp_pc = regcache_read_pc (regcache);
                  if (breakpoint_inserted_here_p (tmp_pc))
                    {
                      if (record_debug)
                        fprintf_unfiltered (gdb_stdlog,
                                            "Process record: break "
                                            "at 0x%s.\n",
                                            paddr_nz (tmp_pc));
                      if (gdbarch_decr_pc_after_break (get_regcache_arch (regcache))
                          && execution_direction == EXEC_FORWARD
                          && !record_resume_step)
                        regcache_write_pc (regcache,
                                           tmp_pc +
                                           gdbarch_decr_pc_after_break
                                           (get_regcache_arch (regcache)));
                      continue_flag = 0;
                    }
                }
            }

          if (continue_flag)
            {
              if (execution_direction == EXEC_REVERSE)
                {
                  if (record_list->prev)
                    record_list = record_list->prev;
                }
              else
                {
                  if (record_list->next)
                    record_list = record_list->next;
                }
            }
        }
      while (continue_flag);

      signal (SIGINT, handle_sigint);

replay_out:
      if (record_get_sig)
        status->value.sig = TARGET_SIGNAL_INT;
      else
        status->value.sig = TARGET_SIGNAL_TRAP;

      discard_cleanups (old_cleanups);
    }

  do_cleanups (set_cleanups);
  return inferior_ptid;
}

static void
record_disconnect (struct target_ops *target, char *args, int from_tty)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: record_disconnect\n");

  unpush_target (&record_ops);
  target_disconnect (args, from_tty);
}

static void
record_detach (struct target_ops *ops, char *args, int from_tty)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: record_detach\n");

  unpush_target (&record_ops);
  target_detach (args, from_tty);
}

static void
record_mourn_inferior (struct target_ops *ops)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: "
                                    "record_mourn_inferior\n");

  unpush_target (&record_ops);
  target_mourn_inferior ();
}

/* Close process record target before killing the inferior process.  */

static void
record_kill (struct target_ops *ops)
{
  if (record_debug)
    fprintf_unfiltered (gdb_stdlog, "Process record: record_kill\n");

  unpush_target (&record_ops);
  target_kill ();
}

/* Record registers change (by user or by GDB) to list as an instruction.  */

static void
record_registers_change (struct regcache *regcache, int regnum)
{
  /* Check record_insn_num.  */
  record_check_insn_num (0);

  record_arch_list_head = NULL;
  record_arch_list_tail = NULL;

  if (regnum < 0)
    {
      int i;
      for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
        {
          if (record_arch_list_add_reg (regcache, i))
            {
              record_list_release (record_arch_list_tail);
              error (_("Process record: failed to record execution log."));
            }
        }
    }
  else
    {
      if (record_arch_list_add_reg (regcache, regnum))
        {
          record_list_release (record_arch_list_tail);
          error (_("Process record: failed to record execution log."));
        }
    }
  if (record_arch_list_add_end ())
    {
      record_list_release (record_arch_list_tail);
      error (_("Process record: failed to record execution log."));
    }
  record_list->next = record_arch_list_head;
  record_arch_list_head->prev = record_list;
  record_list = record_arch_list_tail;

  if (record_insn_num == record_insn_max_num && record_insn_max_num)
    record_list_release_first ();
  else
    record_insn_num++;
}

static void
record_store_registers (struct target_ops *ops, struct regcache *regcache,
                        int regno)
{
  if (!record_gdb_operation_disable)
    {
      if (RECORD_IS_REPLAY)
        {
          int n;
          struct cleanup *old_cleanups;

          /* Let user choose if he wants to write register or not.  */
          if (regno < 0)
            n =
              nquery (_("Because GDB is in replay mode, changing the "
                        "value of a register will make the execution "
                        "log unusable from this point onward.  "
                        "Change all registers?"));
          else
            n =
              nquery (_("Because GDB is in replay mode, changing the value "
                        "of a register will make the execution log unusable "
                        "from this point onward.  Change register %s?"),
                      gdbarch_register_name (get_regcache_arch (regcache),
                                               regno));

          if (!n)
            {
              /* Invalidate the value of regcache that was set in function
                 "regcache_raw_write".  */
              if (regno < 0)
                {
                  int i;
                  for (i = 0;
                       i < gdbarch_num_regs (get_regcache_arch (regcache));
                       i++)
                    regcache_invalidate (regcache, i);
                }
              else
                regcache_invalidate (regcache, regno);

              error (_("Process record canceled the operation."));
            }

          /* Destroy the record from here forward.  */
          record_list_release_next ();
        }

      record_registers_change (regcache, regno);
    }
  record_beneath_to_store_registers (record_beneath_to_store_registers_ops,
                                     regcache, regno);
}

/* Behavior is conditional on RECORD_IS_REPLAY.
   In replay mode, we cannot write memory unles we are willing to
   invalidate the record/replay log from this point forward.  */

static LONGEST
record_xfer_partial (struct target_ops *ops, enum target_object object,
                     const char *annex, gdb_byte *readbuf,
                     const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
{
  if (!record_gdb_operation_disable
      && (object == TARGET_OBJECT_MEMORY
          || object == TARGET_OBJECT_RAW_MEMORY) && writebuf)
    {
      if (RECORD_IS_REPLAY)
        {
          /* Let user choose if he wants to write memory or not.  */
          if (!nquery (_("Because GDB is in replay mode, writing to memory "
                         "will make the execution log unusable from this "
                         "point onward.  Write memory at address 0x%s?"),
                       paddr_nz (offset)))
            return -1;

          /* Destroy the record from here forward.  */
          record_list_release_next ();
        }

      /* Check record_insn_num */
      record_check_insn_num (0);

      /* Record registers change to list as an instruction.  */
      record_arch_list_head = NULL;
      record_arch_list_tail = NULL;
      if (record_arch_list_add_mem (offset, len))
        {
          record_list_release (record_arch_list_tail);
          if (record_debug)
            fprintf_unfiltered (gdb_stdlog,
                                _("Process record: failed to record "
                                  "execution log."));
          return -1;
        }
      if (record_arch_list_add_end ())
        {
          record_list_release (record_arch_list_tail);
          if (record_debug)
            fprintf_unfiltered (gdb_stdlog,
                                _("Process record: failed to record "
                                  "execution log."));
          return -1;
        }
      record_list->next = record_arch_list_head;
      record_arch_list_head->prev = record_list;
      record_list = record_arch_list_tail;

      if (record_insn_num == record_insn_max_num && record_insn_max_num)
        record_list_release_first ();
      else
        record_insn_num++;
    }

  return record_beneath_to_xfer_partial (record_beneath_to_xfer_partial_ops,
                                         object, annex, readbuf, writebuf,
                                         offset, len);
}

/* Behavior is conditional on RECORD_IS_REPLAY.
   We will not actually insert or remove breakpoints when replaying,
   nor when recording.  */

static int
record_insert_breakpoint (struct bp_target_info *bp_tgt)
{
  if (!RECORD_IS_REPLAY)
    {
      struct cleanup *old_cleanups = record_gdb_operation_disable_set ();
      int ret = record_beneath_to_insert_breakpoint (bp_tgt);

      do_cleanups (old_cleanups);

      return ret;
    }

  return 0;
}

static int
record_remove_breakpoint (struct bp_target_info *bp_tgt)
{
  if (!RECORD_IS_REPLAY)
    {
      struct cleanup *old_cleanups = record_gdb_operation_disable_set ();
      int ret = record_beneath_to_remove_breakpoint (bp_tgt);

      do_cleanups (old_cleanups);

      return ret;
    }

  return 0;
}

static int
record_can_execute_reverse (void)
{
  return 1;
}

static void
init_record_ops (void)
{
  record_ops.to_shortname = "record";
  record_ops.to_longname = "Process record and replay target";
  record_ops.to_doc =
    "Log program while executing and replay execution from log.";
  record_ops.to_open = record_open;
  record_ops.to_close = record_close;
  record_ops.to_resume = record_resume;
  record_ops.to_wait = record_wait;
  record_ops.to_disconnect = record_disconnect;
  record_ops.to_detach = record_detach;
  record_ops.to_mourn_inferior = record_mourn_inferior;
  record_ops.to_kill = record_kill;
  record_ops.to_create_inferior = find_default_create_inferior;
  record_ops.to_store_registers = record_store_registers;
  record_ops.to_xfer_partial = record_xfer_partial;
  record_ops.to_insert_breakpoint = record_insert_breakpoint;
  record_ops.to_remove_breakpoint = record_remove_breakpoint;
  record_ops.to_can_execute_reverse = record_can_execute_reverse;
  record_ops.to_stratum = record_stratum;
  record_ops.to_magic = OPS_MAGIC;
}

static void
show_record_debug (struct ui_file *file, int from_tty,
                   struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Debugging of process record target is %s.\n"),
                    value);
}

/* Alias for "target record".  */

static void
cmd_record_start (char *args, int from_tty)
{
  execute_command ("target record", from_tty);
}

/* Truncate the record log from the present point
   of replay until the end.  */

static void
cmd_record_delete (char *args, int from_tty)
{
  if (current_target.to_stratum == record_stratum)
    {
      if (RECORD_IS_REPLAY)
        {
          if (!from_tty || query (_("Delete the log from this point forward "
                                    "and begin to record the running message "
                                    "at current PC?")))
            record_list_release_next ();
        }
      else
          printf_unfiltered (_("Already at end of record list.\n"));

    }
  else
    printf_unfiltered (_("Process record is not started.\n"));
}

/* Implement the "stoprecord" command.  */

static void
cmd_record_stop (char *args, int from_tty)
{
  if (current_target.to_stratum == record_stratum)
    {
      if (!record_list || !from_tty || query (_("Delete recorded log and "
                                                "stop recording?")))
        unpush_target (&record_ops);
    }
  else
    printf_unfiltered (_("Process record is not started.\n"));
}

/* Set upper limit of record log size.  */

static void
set_record_insn_max_num (char *args, int from_tty, struct cmd_list_element *c)
{
  if (record_insn_num > record_insn_max_num && record_insn_max_num)
    {
      printf_unfiltered (_("Record instructions number is bigger than "
                           "record instructions max number.  Auto delete "
                           "the first ones?\n"));

      while (record_insn_num > record_insn_max_num)
        record_list_release_first ();
    }
}

/* Print the current index into the record log (number of insns recorded
   so far).  */

static void
show_record_insn_number (char *ignore, int from_tty)
{
  printf_unfiltered (_("Record instruction number is %d.\n"),
                     record_insn_num);
}

static struct cmd_list_element *record_cmdlist, *set_record_cmdlist,
                               *show_record_cmdlist, *info_record_cmdlist;

static void
set_record_command (char *args, int from_tty)
{
  printf_unfiltered (_("\
\"set record\" must be followed by an apporpriate subcommand.\n"));
  help_list (set_record_cmdlist, "set record ", all_commands, gdb_stdout);
}

static void
show_record_command (char *args, int from_tty)
{
  cmd_show_list (show_record_cmdlist, from_tty, "");
}

static void
info_record_command (char *args, int from_tty)
{
  cmd_show_list (info_record_cmdlist, from_tty, "");
}

void
_initialize_record (void)
{
  /* Init record_first.  */
  record_first.prev = NULL;
  record_first.next = NULL;
  record_first.type = record_end;

  init_record_ops ();
  add_target (&record_ops);

  add_setshow_zinteger_cmd ("record", no_class, &record_debug,
                            _("Set debugging of record/replay feature."),
                            _("Show debugging of record/replay feature."),
                            _("When enabled, debugging output for "
                              "record/replay feature is displayed."),
                            NULL, show_record_debug, &setdebuglist,
                            &showdebuglist);

  add_prefix_cmd ("record", class_obscure, cmd_record_start,
                  _("Abbreviated form of \"target record\" command."),
                  &record_cmdlist, "record ", 0, &cmdlist);
  add_com_alias ("rec", "record", class_obscure, 1);
  add_prefix_cmd ("record", class_support, set_record_command,
                  _("Set record options"), &set_record_cmdlist,
                  "set record ", 0, &setlist);
  add_alias_cmd ("rec", "record", class_obscure, 1, &setlist);
  add_prefix_cmd ("record", class_support, show_record_command,
                  _("Show record options"), &show_record_cmdlist,
                  "show record ", 0, &showlist);
  add_alias_cmd ("rec", "record", class_obscure, 1, &showlist);
  add_prefix_cmd ("record", class_support, info_record_command,
                  _("Info record options"), &info_record_cmdlist,
                  "info record ", 0, &infolist);
  add_alias_cmd ("rec", "record", class_obscure, 1, &infolist);


  add_cmd ("delete", class_obscure, cmd_record_delete,
           _("Delete the rest of execution log and start recording it anew."),
           &record_cmdlist);
  add_alias_cmd ("d", "delete", class_obscure, 1, &record_cmdlist);
  add_alias_cmd ("del", "delete", class_obscure, 1, &record_cmdlist);

  add_cmd ("stop", class_obscure, cmd_record_stop,
           _("Stop the record/replay target."),
           &record_cmdlist);
  add_alias_cmd ("s", "stop", class_obscure, 1, &record_cmdlist);

  /* Record instructions number limit command.  */
  add_setshow_boolean_cmd ("stop-at-limit", no_class,
                            &record_stop_at_limit, _("\
Set whether record/replay stops when record/replay buffer becomes full."), _("\
Show whether record/replay stops when record/replay buffer becomes full."), _("\
Default is ON.\n\
When ON, if the record/replay buffer becomes full, ask user what to do.\n\
When OFF, if the record/replay buffer becomes full,\n\
delete the oldest recorded instruction to make room for each new one."),
                            NULL, NULL,
                            &set_record_cmdlist, &show_record_cmdlist);
  add_setshow_zinteger_cmd ("insn-number-max", no_class,
                            &record_insn_max_num,
                            _("Set record/replay buffer limit."),
                            _("Show record/replay buffer limit."), _("\
Set the maximum number of instructions to be stored in the\n\
record/replay buffer.  Zero means unlimited.  Default is 200000."),
                            set_record_insn_max_num,
                            NULL, &set_record_cmdlist, &show_record_cmdlist);
  add_cmd ("insn-number", class_obscure, show_record_insn_number,
            _("Show the current number of instructions in the "
              "record/replay buffer."), &info_record_cmdlist);
}