clang-tests-external/gdb/7.5/gdb/infrun.c

/* Target-struct-independent code to start (run) and stop an inferior
   process.

   Copyright (C) 1986-2012 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 "gdb_string.h"
#include <ctype.h>
#include "symtab.h"
#include "frame.h"
#include "inferior.h"
#include "exceptions.h"
#include "breakpoint.h"
#include "gdb_wait.h"
#include "gdbcore.h"
#include "gdbcmd.h"
#include "cli/cli-script.h"
#include "target.h"
#include "gdbthread.h"
#include "annotate.h"
#include "symfile.h"
#include "top.h"
#include <signal.h>
#include "inf-loop.h"
#include "regcache.h"
#include "value.h"
#include "observer.h"
#include "language.h"
#include "solib.h"
#include "main.h"
#include "dictionary.h"
#include "block.h"
#include "gdb_assert.h"
#include "mi/mi-common.h"
#include "event-top.h"
#include "record.h"
#include "inline-frame.h"
#include "jit.h"
#include "tracepoint.h"
#include "continuations.h"
#include "interps.h"
#include "skip.h"
#include "probe.h"
#include "objfiles.h"

/* Prototypes for local functions */

static void signals_info (char *, int);

static void handle_command (char *, int);

static void sig_print_info (enum gdb_signal);

static void sig_print_header (void);

static void resume_cleanups (void *);

static int hook_stop_stub (void *);

static int restore_selected_frame (void *);

static int follow_fork (void);

static void set_schedlock_func (char *args, int from_tty,
				struct cmd_list_element *c);

static int currently_stepping (struct thread_info *tp);

static int currently_stepping_or_nexting_callback (struct thread_info *tp,
						   void *data);

static void xdb_handle_command (char *args, int from_tty);

static int prepare_to_proceed (int);

static void print_exited_reason (int exitstatus);

static void print_signal_exited_reason (enum gdb_signal siggnal);

static void print_no_history_reason (void);

static void print_signal_received_reason (enum gdb_signal siggnal);

static void print_end_stepping_range_reason (void);

void _initialize_infrun (void);

void nullify_last_target_wait_ptid (void);

static void insert_hp_step_resume_breakpoint_at_frame (struct frame_info *);

static void insert_step_resume_breakpoint_at_caller (struct frame_info *);

static void insert_longjmp_resume_breakpoint (struct gdbarch *, CORE_ADDR);

/* When set, stop the 'step' command if we enter a function which has
   no line number information.  The normal behavior is that we step
   over such function.  */
int step_stop_if_no_debug = 0;
static void
show_step_stop_if_no_debug (struct ui_file *file, int from_tty,
			    struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Mode of the step operation is %s.\n"), value);
}

/* In asynchronous mode, but simulating synchronous execution.  */

int sync_execution = 0;

/* wait_for_inferior and normal_stop use this to notify the user
   when the inferior stopped in a different thread than it had been
   running in.  */

static ptid_t previous_inferior_ptid;

/* Default behavior is to detach newly forked processes (legacy).  */
int detach_fork = 1;

int debug_displaced = 0;
static void
show_debug_displaced (struct ui_file *file, int from_tty,
		      struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Displace stepping debugging is %s.\n"), value);
}

int debug_infrun = 0;
static void
show_debug_infrun (struct ui_file *file, int from_tty,
		   struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Inferior debugging is %s.\n"), value);
}


/* Support for disabling address space randomization.  */

int disable_randomization = 1;

static void
show_disable_randomization (struct ui_file *file, int from_tty,
			    struct cmd_list_element *c, const char *value)
{
  if (target_supports_disable_randomization ())
    fprintf_filtered (file,
		      _("Disabling randomization of debuggee's "
			"virtual address space is %s.\n"),
		      value);
  else
    fputs_filtered (_("Disabling randomization of debuggee's "
		      "virtual address space is unsupported on\n"
		      "this platform.\n"), file);
}

static void
set_disable_randomization (char *args, int from_tty,
			   struct cmd_list_element *c)
{
  if (!target_supports_disable_randomization ())
    error (_("Disabling randomization of debuggee's "
	     "virtual address space is unsupported on\n"
	     "this platform."));
}


/* If the program uses ELF-style shared libraries, then calls to
   functions in shared libraries go through stubs, which live in a
   table called the PLT (Procedure Linkage Table).  The first time the
   function is called, the stub sends control to the dynamic linker,
   which looks up the function's real address, patches the stub so
   that future calls will go directly to the function, and then passes
   control to the function.

   If we are stepping at the source level, we don't want to see any of
   this --- we just want to skip over the stub and the dynamic linker.
   The simple approach is to single-step until control leaves the
   dynamic linker.

   However, on some systems (e.g., Red Hat's 5.2 distribution) the
   dynamic linker calls functions in the shared C library, so you
   can't tell from the PC alone whether the dynamic linker is still
   running.  In this case, we use a step-resume breakpoint to get us
   past the dynamic linker, as if we were using "next" to step over a
   function call.

   in_solib_dynsym_resolve_code() says whether we're in the dynamic
   linker code or not.  Normally, this means we single-step.  However,
   if SKIP_SOLIB_RESOLVER then returns non-zero, then its value is an
   address where we can place a step-resume breakpoint to get past the
   linker's symbol resolution function.

   in_solib_dynsym_resolve_code() can generally be implemented in a
   pretty portable way, by comparing the PC against the address ranges
   of the dynamic linker's sections.

   SKIP_SOLIB_RESOLVER is generally going to be system-specific, since
   it depends on internal details of the dynamic linker.  It's usually
   not too hard to figure out where to put a breakpoint, but it
   certainly isn't portable.  SKIP_SOLIB_RESOLVER should do plenty of
   sanity checking.  If it can't figure things out, returning zero and
   getting the (possibly confusing) stepping behavior is better than
   signalling an error, which will obscure the change in the
   inferior's state.  */

/* This function returns TRUE if pc is the address of an instruction
   that lies within the dynamic linker (such as the event hook, or the
   dld itself).

   This function must be used only when a dynamic linker event has
   been caught, and the inferior is being stepped out of the hook, or
   undefined results are guaranteed.  */

#ifndef SOLIB_IN_DYNAMIC_LINKER
#define SOLIB_IN_DYNAMIC_LINKER(pid,pc) 0
#endif

/* "Observer mode" is somewhat like a more extreme version of
   non-stop, in which all GDB operations that might affect the
   target's execution have been disabled.  */

static int non_stop_1 = 0;

int observer_mode = 0;
static int observer_mode_1 = 0;

static void
set_observer_mode (char *args, int from_tty,
		   struct cmd_list_element *c)
{
  extern int pagination_enabled;

  if (target_has_execution)
    {
      observer_mode_1 = observer_mode;
      error (_("Cannot change this setting while the inferior is running."));
    }

  observer_mode = observer_mode_1;

  may_write_registers = !observer_mode;
  may_write_memory = !observer_mode;
  may_insert_breakpoints = !observer_mode;
  may_insert_tracepoints = !observer_mode;
  /* We can insert fast tracepoints in or out of observer mode,
     but enable them if we're going into this mode.  */
  if (observer_mode)
    may_insert_fast_tracepoints = 1;
  may_stop = !observer_mode;
  update_target_permissions ();

  /* Going *into* observer mode we must force non-stop, then
     going out we leave it that way.  */
  if (observer_mode)
    {
      target_async_permitted = 1;
      pagination_enabled = 0;
      non_stop = non_stop_1 = 1;
    }

  if (from_tty)
    printf_filtered (_("Observer mode is now %s.\n"),
		     (observer_mode ? "on" : "off"));
}

static void
show_observer_mode (struct ui_file *file, int from_tty,
		    struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Observer mode is %s.\n"), value);
}

/* This updates the value of observer mode based on changes in
   permissions.  Note that we are deliberately ignoring the values of
   may-write-registers and may-write-memory, since the user may have
   reason to enable these during a session, for instance to turn on a
   debugging-related global.  */

void
update_observer_mode (void)
{
  int newval;

  newval = (!may_insert_breakpoints
	    && !may_insert_tracepoints
	    && may_insert_fast_tracepoints
	    && !may_stop
	    && non_stop);

  /* Let the user know if things change.  */
  if (newval != observer_mode)
    printf_filtered (_("Observer mode is now %s.\n"),
		     (newval ? "on" : "off"));

  observer_mode = observer_mode_1 = newval;
}

/* Tables of how to react to signals; the user sets them.  */

static unsigned char *signal_stop;
static unsigned char *signal_print;
static unsigned char *signal_program;

/* Table of signals that the target may silently handle.
   This is automatically determined from the flags above,
   and simply cached here.  */
static unsigned char *signal_pass;

#define SET_SIGS(nsigs,sigs,flags) \
  do { \
    int signum = (nsigs); \
    while (signum-- > 0) \
      if ((sigs)[signum]) \
	(flags)[signum] = 1; \
  } while (0)

#define UNSET_SIGS(nsigs,sigs,flags) \
  do { \
    int signum = (nsigs); \
    while (signum-- > 0) \
      if ((sigs)[signum]) \
	(flags)[signum] = 0; \
  } while (0)

/* Update the target's copy of SIGNAL_PROGRAM.  The sole purpose of
   this function is to avoid exporting `signal_program'.  */

void
update_signals_program_target (void)
{
  target_program_signals ((int) GDB_SIGNAL_LAST, signal_program);
}

/* Value to pass to target_resume() to cause all threads to resume.  */

#define RESUME_ALL minus_one_ptid

/* Command list pointer for the "stop" placeholder.  */

static struct cmd_list_element *stop_command;

/* Function inferior was in as of last step command.  */

static struct symbol *step_start_function;

/* Nonzero if we want to give control to the user when we're notified
   of shared library events by the dynamic linker.  */
int stop_on_solib_events;
static void
show_stop_on_solib_events (struct ui_file *file, int from_tty,
			   struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Stopping for shared library events is %s.\n"),
		    value);
}

/* Nonzero means expecting a trace trap
   and should stop the inferior and return silently when it happens.  */

int stop_after_trap;

/* Save register contents here when executing a "finish" command or are
   about to pop a stack dummy frame, if-and-only-if proceed_to_finish is set.
   Thus this contains the return value from the called function (assuming
   values are returned in a register).  */

struct regcache *stop_registers;

/* Nonzero after stop if current stack frame should be printed.  */

static int stop_print_frame;

/* This is a cached copy of the pid/waitstatus of the last event
   returned by target_wait()/deprecated_target_wait_hook().  This
   information is returned by get_last_target_status().  */
static ptid_t target_last_wait_ptid;
static struct target_waitstatus target_last_waitstatus;

static void context_switch (ptid_t ptid);

void init_thread_stepping_state (struct thread_info *tss);

void init_infwait_state (void);

static const char follow_fork_mode_child[] = "child";
static const char follow_fork_mode_parent[] = "parent";

static const char *const follow_fork_mode_kind_names[] = {
  follow_fork_mode_child,
  follow_fork_mode_parent,
  NULL
};

static const char *follow_fork_mode_string = follow_fork_mode_parent;
static void
show_follow_fork_mode_string (struct ui_file *file, int from_tty,
			      struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
		    _("Debugger response to a program "
		      "call of fork or vfork is \"%s\".\n"),
		    value);
}


/* Tell the target to follow the fork we're stopped at.  Returns true
   if the inferior should be resumed; false, if the target for some
   reason decided it's best not to resume.  */

static int
follow_fork (void)
{
  int follow_child = (follow_fork_mode_string == follow_fork_mode_child);
  int should_resume = 1;
  struct thread_info *tp;

  /* Copy user stepping state to the new inferior thread.  FIXME: the
     followed fork child thread should have a copy of most of the
     parent thread structure's run control related fields, not just these.
     Initialized to avoid "may be used uninitialized" warnings from gcc.  */
  struct breakpoint *step_resume_breakpoint = NULL;
  struct breakpoint *exception_resume_breakpoint = NULL;
  CORE_ADDR step_range_start = 0;
  CORE_ADDR step_range_end = 0;
  struct frame_id step_frame_id = { 0 };

  if (!non_stop)
    {
      ptid_t wait_ptid;
      struct target_waitstatus wait_status;

      /* Get the last target status returned by target_wait().  */
      get_last_target_status (&wait_ptid, &wait_status);

      /* If not stopped at a fork event, then there's nothing else to
	 do.  */
      if (wait_status.kind != TARGET_WAITKIND_FORKED
	  && wait_status.kind != TARGET_WAITKIND_VFORKED)
	return 1;

      /* Check if we switched over from WAIT_PTID, since the event was
	 reported.  */
      if (!ptid_equal (wait_ptid, minus_one_ptid)
	  && !ptid_equal (inferior_ptid, wait_ptid))
	{
	  /* We did.  Switch back to WAIT_PTID thread, to tell the
	     target to follow it (in either direction).  We'll
	     afterwards refuse to resume, and inform the user what
	     happened.  */
	  switch_to_thread (wait_ptid);
	  should_resume = 0;
	}
    }

  tp = inferior_thread ();

  /* If there were any forks/vforks that were caught and are now to be
     followed, then do so now.  */
  switch (tp->pending_follow.kind)
    {
    case TARGET_WAITKIND_FORKED:
    case TARGET_WAITKIND_VFORKED:
      {
	ptid_t parent, child;

	/* If the user did a next/step, etc, over a fork call,
	   preserve the stepping state in the fork child.  */
	if (follow_child && should_resume)
	  {
	    step_resume_breakpoint = clone_momentary_breakpoint
					 (tp->control.step_resume_breakpoint);
	    step_range_start = tp->control.step_range_start;
	    step_range_end = tp->control.step_range_end;
	    step_frame_id = tp->control.step_frame_id;
	    exception_resume_breakpoint
	      = clone_momentary_breakpoint (tp->control.exception_resume_breakpoint);

	    /* For now, delete the parent's sr breakpoint, otherwise,
	       parent/child sr breakpoints are considered duplicates,
	       and the child version will not be installed.  Remove
	       this when the breakpoints module becomes aware of
	       inferiors and address spaces.  */
	    delete_step_resume_breakpoint (tp);
	    tp->control.step_range_start = 0;
	    tp->control.step_range_end = 0;
	    tp->control.step_frame_id = null_frame_id;
	    delete_exception_resume_breakpoint (tp);
	  }

	parent = inferior_ptid;
	child = tp->pending_follow.value.related_pid;

	/* Tell the target to do whatever is necessary to follow
	   either parent or child.  */
	if (target_follow_fork (follow_child))
	  {
	    /* Target refused to follow, or there's some other reason
	       we shouldn't resume.  */
	    should_resume = 0;
	  }
	else
	  {
	    /* This pending follow fork event is now handled, one way
	       or another.  The previous selected thread may be gone
	       from the lists by now, but if it is still around, need
	       to clear the pending follow request.  */
	    tp = find_thread_ptid (parent);
	    if (tp)
	      tp->pending_follow.kind = TARGET_WAITKIND_SPURIOUS;

	    /* This makes sure we don't try to apply the "Switched
	       over from WAIT_PID" logic above.  */
	    nullify_last_target_wait_ptid ();

	    /* If we followed the child, switch to it...  */
	    if (follow_child)
	      {
		switch_to_thread (child);

		/* ... and preserve the stepping state, in case the
		   user was stepping over the fork call.  */
		if (should_resume)
		  {
		    tp = inferior_thread ();
		    tp->control.step_resume_breakpoint
		      = step_resume_breakpoint;
		    tp->control.step_range_start = step_range_start;
		    tp->control.step_range_end = step_range_end;
		    tp->control.step_frame_id = step_frame_id;
		    tp->control.exception_resume_breakpoint
		      = exception_resume_breakpoint;
		  }
		else
		  {
		    /* If we get here, it was because we're trying to
		       resume from a fork catchpoint, but, the user
		       has switched threads away from the thread that
		       forked.  In that case, the resume command
		       issued is most likely not applicable to the
		       child, so just warn, and refuse to resume.  */
		    warning (_("Not resuming: switched threads "
			       "before following fork child.\n"));
		  }

		/* Reset breakpoints in the child as appropriate.  */
		follow_inferior_reset_breakpoints ();
	      }
	    else
	      switch_to_thread (parent);
	  }
      }
      break;
    case TARGET_WAITKIND_SPURIOUS:
      /* Nothing to follow.  */
      break;
    default:
      internal_error (__FILE__, __LINE__,
		      "Unexpected pending_follow.kind %d\n",
		      tp->pending_follow.kind);
      break;
    }

  return should_resume;
}

void
follow_inferior_reset_breakpoints (void)
{
  struct thread_info *tp = inferior_thread ();

  /* Was there a step_resume breakpoint?  (There was if the user
     did a "next" at the fork() call.)  If so, explicitly reset its
     thread number.

     step_resumes are a form of bp that are made to be per-thread.
     Since we created the step_resume bp when the parent process
     was being debugged, and now are switching to the child process,
     from the breakpoint package's viewpoint, that's a switch of
     "threads".  We must update the bp's notion of which thread
     it is for, or it'll be ignored when it triggers.  */

  if (tp->control.step_resume_breakpoint)
    breakpoint_re_set_thread (tp->control.step_resume_breakpoint);

  if (tp->control.exception_resume_breakpoint)
    breakpoint_re_set_thread (tp->control.exception_resume_breakpoint);

  /* Reinsert all breakpoints in the child.  The user may have set
     breakpoints after catching the fork, in which case those
     were never set in the child, but only in the parent.  This makes
     sure the inserted breakpoints match the breakpoint list.  */

  breakpoint_re_set ();
  insert_breakpoints ();
}

/* The child has exited or execed: resume threads of the parent the
   user wanted to be executing.  */

static int
proceed_after_vfork_done (struct thread_info *thread,
			  void *arg)
{
  int pid = * (int *) arg;

  if (ptid_get_pid (thread->ptid) == pid
      && is_running (thread->ptid)
      && !is_executing (thread->ptid)
      && !thread->stop_requested
      && thread->suspend.stop_signal == GDB_SIGNAL_0)
    {
      if (debug_infrun)
	fprintf_unfiltered (gdb_stdlog,
			    "infrun: resuming vfork parent thread %s\n",
			    target_pid_to_str (thread->ptid));

      switch_to_thread (thread->ptid);
      clear_proceed_status ();
      proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
    }

  return 0;
}

/* Called whenever we notice an exec or exit event, to handle
   detaching or resuming a vfork parent.  */

static void
handle_vfork_child_exec_or_exit (int exec)
{
  struct inferior *inf = current_inferior ();

  if (inf->vfork_parent)
    {
      int resume_parent = -1;

      /* This exec or exit marks the end of the shared memory region
	 between the parent and the child.  If the user wanted to
	 detach from the parent, now is the time.  */

      if (inf->vfork_parent->pending_detach)
	{
	  struct thread_info *tp;
	  struct cleanup *old_chain;
	  struct program_space *pspace;
	  struct address_space *aspace;

	  /* follow-fork child, detach-on-fork on.  */

	  old_chain = make_cleanup_restore_current_thread ();

	  /* We're letting loose of the parent.  */
	  tp = any_live_thread_of_process (inf->vfork_parent->pid);
	  switch_to_thread (tp->ptid);

	  /* We're about to detach from the parent, which implicitly
	     removes breakpoints from its address space.  There's a
	     catch here: we want to reuse the spaces for the child,
	     but, parent/child are still sharing the pspace at this
	     point, although the exec in reality makes the kernel give
	     the child a fresh set of new pages.  The problem here is
	     that the breakpoints module being unaware of this, would
	     likely chose the child process to write to the parent
	     address space.  Swapping the child temporarily away from
	     the spaces has the desired effect.  Yes, this is "sort
	     of" a hack.  */

	  pspace = inf->pspace;
	  aspace = inf->aspace;
	  inf->aspace = NULL;
	  inf->pspace = NULL;

	  if (debug_infrun || info_verbose)
	    {
	      target_terminal_ours ();

	      if (exec)
		fprintf_filtered (gdb_stdlog,
				  "Detaching vfork parent process "
				  "%d after child exec.\n",
				  inf->vfork_parent->pid);
	      else
		fprintf_filtered (gdb_stdlog,
				  "Detaching vfork parent process "
				  "%d after child exit.\n",
				  inf->vfork_parent->pid);
	    }

	  target_detach (NULL, 0);

	  /* Put it back.  */
	  inf->pspace = pspace;
	  inf->aspace = aspace;

	  do_cleanups (old_chain);
	}
      else if (exec)
	{
	  /* We're staying attached to the parent, so, really give the
	     child a new address space.  */
	  inf->pspace = add_program_space (maybe_new_address_space ());
	  inf->aspace = inf->pspace->aspace;
	  inf->removable = 1;
	  set_current_program_space (inf->pspace);

	  resume_parent = inf->vfork_parent->pid;

	  /* Break the bonds.  */
	  inf->vfork_parent->vfork_child = NULL;
	}
      else
	{
	  struct cleanup *old_chain;
	  struct program_space *pspace;

	  /* If this is a vfork child exiting, then the pspace and
	     aspaces were shared with the parent.  Since we're
	     reporting the process exit, we'll be mourning all that is
	     found in the address space, and switching to null_ptid,
	     preparing to start a new inferior.  But, since we don't
	     want to clobber the parent's address/program spaces, we
	     go ahead and create a new one for this exiting
	     inferior.  */

	  /* Switch to null_ptid, so that clone_program_space doesn't want
	     to read the selected frame of a dead process.  */
	  old_chain = save_inferior_ptid ();
	  inferior_ptid = null_ptid;

	  /* This inferior is dead, so avoid giving the breakpoints
	     module the option to write through to it (cloning a
	     program space resets breakpoints).  */
	  inf->aspace = NULL;
	  inf->pspace = NULL;
	  pspace = add_program_space (maybe_new_address_space ());
	  set_current_program_space (pspace);
	  inf->removable = 1;
	  inf->symfile_flags = SYMFILE_NO_READ;
	  clone_program_space (pspace, inf->vfork_parent->pspace);
	  inf->pspace = pspace;
	  inf->aspace = pspace->aspace;

	  /* Put back inferior_ptid.  We'll continue mourning this
	     inferior.  */
	  do_cleanups (old_chain);

	  resume_parent = inf->vfork_parent->pid;
	  /* Break the bonds.  */
	  inf->vfork_parent->vfork_child = NULL;
	}

      inf->vfork_parent = NULL;

      gdb_assert (current_program_space == inf->pspace);

      if (non_stop && resume_parent != -1)
	{
	  /* If the user wanted the parent to be running, let it go
	     free now.  */
	  struct cleanup *old_chain = make_cleanup_restore_current_thread ();

	  if (debug_infrun)
	    fprintf_unfiltered (gdb_stdlog,
				"infrun: resuming vfork parent process %d\n",
				resume_parent);

	  iterate_over_threads (proceed_after_vfork_done, &resume_parent);

	  do_cleanups (old_chain);
	}
    }
}

/* Enum strings for "set|show displaced-stepping".  */

static const char follow_exec_mode_new[] = "new";
static const char follow_exec_mode_same[] = "same";
static const char *const follow_exec_mode_names[] =
{
  follow_exec_mode_new,
  follow_exec_mode_same,
  NULL,
};

static const char *follow_exec_mode_string = follow_exec_mode_same;
static void
show_follow_exec_mode_string (struct ui_file *file, int from_tty,
			      struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Follow exec mode is \"%s\".\n"),  value);
}

/* EXECD_PATHNAME is assumed to be non-NULL.  */

static void
follow_exec (ptid_t pid, char *execd_pathname)
{
  struct thread_info *th = inferior_thread ();
  struct inferior *inf = current_inferior ();

  /* This is an exec event that we actually wish to pay attention to.
     Refresh our symbol table to the newly exec'd program, remove any
     momentary bp's, etc.

     If there are breakpoints, they aren't really inserted now,
     since the exec() transformed our inferior into a fresh set
     of instructions.

     We want to preserve symbolic breakpoints on the list, since
     we have hopes that they can be reset after the new a.out's
     symbol table is read.

     However, any "raw" breakpoints must be removed from the list
     (e.g., the solib bp's), since their address is probably invalid
     now.

     And, we DON'T want to call delete_breakpoints() here, since
     that may write the bp's "shadow contents" (the instruction
     value that was overwritten witha TRAP instruction).  Since
     we now have a new a.out, those shadow contents aren't valid.  */

  mark_breakpoints_out ();

  update_breakpoints_after_exec ();

  /* If there was one, it's gone now.  We cannot truly step-to-next
     statement through an exec().  */
  th->control.step_resume_breakpoint = NULL;
  th->control.exception_resume_breakpoint = NULL;
  th->control.step_range_start = 0;
  th->control.step_range_end = 0;

  /* The target reports the exec event to the main thread, even if
     some other thread does the exec, and even if the main thread was
     already stopped --- if debugging in non-stop mode, it's possible
     the user had the main thread held stopped in the previous image
     --- release it now.  This is the same behavior as step-over-exec
     with scheduler-locking on in all-stop mode.  */
  th->stop_requested = 0;

  /* What is this a.out's name?  */
  printf_unfiltered (_("%s is executing new program: %s\n"),
		     target_pid_to_str (inferior_ptid),
		     execd_pathname);

  /* We've followed the inferior through an exec.  Therefore, the
     inferior has essentially been killed & reborn.  */

  gdb_flush (gdb_stdout);

  breakpoint_init_inferior (inf_execd);

  if (gdb_sysroot && *gdb_sysroot)
    {
      char *name = alloca (strlen (gdb_sysroot)
			    + strlen (execd_pathname)
			    + 1);

      strcpy (name, gdb_sysroot);
      strcat (name, execd_pathname);
      execd_pathname = name;
    }

  /* Reset the shared library package.  This ensures that we get a
     shlib event when the child reaches "_start", at which point the
     dld will have had a chance to initialize the child.  */
  /* Also, loading a symbol file below may trigger symbol lookups, and
     we don't want those to be satisfied by the libraries of the
     previous incarnation of this process.  */
  no_shared_libraries (NULL, 0);

  if (follow_exec_mode_string == follow_exec_mode_new)
    {
      struct program_space *pspace;

      /* The user wants to keep the old inferior and program spaces
	 around.  Create a new fresh one, and switch to it.  */

      inf = add_inferior (current_inferior ()->pid);
      pspace = add_program_space (maybe_new_address_space ());
      inf->pspace = pspace;
      inf->aspace = pspace->aspace;

      exit_inferior_num_silent (current_inferior ()->num);

      set_current_inferior (inf);
      set_current_program_space (pspace);
    }

  gdb_assert (current_program_space == inf->pspace);

  /* That a.out is now the one to use.  */
  exec_file_attach (execd_pathname, 0);

  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
     (Position Independent Executable) main symbol file will get applied by
     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
     the breakpoints with the zero displacement.  */

  symbol_file_add (execd_pathname,
		   (inf->symfile_flags
		    | SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET),
		   NULL, 0);

  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
    set_initial_language ();

#ifdef SOLIB_CREATE_INFERIOR_HOOK
  SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
#else
  solib_create_inferior_hook (0);
#endif

  jit_inferior_created_hook ();

  breakpoint_re_set ();

  /* Reinsert all breakpoints.  (Those which were symbolic have
     been reset to the proper address in the new a.out, thanks
     to symbol_file_command...).  */
  insert_breakpoints ();

  /* The next resume of this inferior should bring it to the shlib
     startup breakpoints.  (If the user had also set bp's on
     "main" from the old (parent) process, then they'll auto-
     matically get reset there in the new process.).  */
}

/* Non-zero if we just simulating a single-step.  This is needed
   because we cannot remove the breakpoints in the inferior process
   until after the `wait' in `wait_for_inferior'.  */
static int singlestep_breakpoints_inserted_p = 0;

/* The thread we inserted single-step breakpoints for.  */
static ptid_t singlestep_ptid;

/* PC when we started this single-step.  */
static CORE_ADDR singlestep_pc;

/* If another thread hit the singlestep breakpoint, we save the original
   thread here so that we can resume single-stepping it later.  */
static ptid_t saved_singlestep_ptid;
static int stepping_past_singlestep_breakpoint;

/* If not equal to null_ptid, this means that after stepping over breakpoint
   is finished, we need to switch to deferred_step_ptid, and step it.

   The use case is when one thread has hit a breakpoint, and then the user 
   has switched to another thread and issued 'step'.  We need to step over
   breakpoint in the thread which hit the breakpoint, but then continue
   stepping the thread user has selected.  */
static ptid_t deferred_step_ptid;

/* Displaced stepping.  */

/* In non-stop debugging mode, we must take special care to manage
   breakpoints properly; in particular, the traditional strategy for
   stepping a thread past a breakpoint it has hit is unsuitable.
   'Displaced stepping' is a tactic for stepping one thread past a
   breakpoint it has hit while ensuring that other threads running
   concurrently will hit the breakpoint as they should.

   The traditional way to step a thread T off a breakpoint in a
   multi-threaded program in all-stop mode is as follows:

   a0) Initially, all threads are stopped, and breakpoints are not
       inserted.
   a1) We single-step T, leaving breakpoints uninserted.
   a2) We insert breakpoints, and resume all threads.

   In non-stop debugging, however, this strategy is unsuitable: we
   don't want to have to stop all threads in the system in order to
   continue or step T past a breakpoint.  Instead, we use displaced
   stepping:

   n0) Initially, T is stopped, other threads are running, and
       breakpoints are inserted.
   n1) We copy the instruction "under" the breakpoint to a separate
       location, outside the main code stream, making any adjustments
       to the instruction, register, and memory state as directed by
       T's architecture.
   n2) We single-step T over the instruction at its new location.
   n3) We adjust the resulting register and memory state as directed
       by T's architecture.  This includes resetting T's PC to point
       back into the main instruction stream.
   n4) We resume T.

   This approach depends on the following gdbarch methods:

   - gdbarch_max_insn_length and gdbarch_displaced_step_location
     indicate where to copy the instruction, and how much space must
     be reserved there.  We use these in step n1.

   - gdbarch_displaced_step_copy_insn copies a instruction to a new
     address, and makes any necessary adjustments to the instruction,
     register contents, and memory.  We use this in step n1.

   - gdbarch_displaced_step_fixup adjusts registers and memory after
     we have successfuly single-stepped the instruction, to yield the
     same effect the instruction would have had if we had executed it
     at its original address.  We use this in step n3.

   - gdbarch_displaced_step_free_closure provides cleanup.

   The gdbarch_displaced_step_copy_insn and
   gdbarch_displaced_step_fixup functions must be written so that
   copying an instruction with gdbarch_displaced_step_copy_insn,
   single-stepping across the copied instruction, and then applying
   gdbarch_displaced_insn_fixup should have the same effects on the
   thread's memory and registers as stepping the instruction in place
   would have.  Exactly which responsibilities fall to the copy and
   which fall to the fixup is up to the author of those functions.

   See the comments in gdbarch.sh for details.

   Note that displaced stepping and software single-step cannot
   currently be used in combination, although with some care I think
   they could be made to.  Software single-step works by placing
   breakpoints on all possible subsequent instructions; if the
   displaced instruction is a PC-relative jump, those breakpoints
   could fall in very strange places --- on pages that aren't
   executable, or at addresses that are not proper instruction
   boundaries.  (We do generally let other threads run while we wait
   to hit the software single-step breakpoint, and they might
   encounter such a corrupted instruction.)  One way to work around
   this would be to have gdbarch_displaced_step_copy_insn fully
   simulate the effect of PC-relative instructions (and return NULL)
   on architectures that use software single-stepping.

   In non-stop mode, we can have independent and simultaneous step
   requests, so more than one thread may need to simultaneously step
   over a breakpoint.  The current implementation assumes there is
   only one scratch space per process.  In this case, we have to
   serialize access to the scratch space.  If thread A wants to step
   over a breakpoint, but we are currently waiting for some other
   thread to complete a displaced step, we leave thread A stopped and
   place it in the displaced_step_request_queue.  Whenever a displaced
   step finishes, we pick the next thread in the queue and start a new
   displaced step operation on it.  See displaced_step_prepare and
   displaced_step_fixup for details.  */

struct displaced_step_request
{
  ptid_t ptid;
  struct displaced_step_request *next;
};

/* Per-inferior displaced stepping state.  */
struct displaced_step_inferior_state
{
  /* Pointer to next in linked list.  */
  struct displaced_step_inferior_state *next;

  /* The process this displaced step state refers to.  */
  int pid;

  /* A queue of pending displaced stepping requests.  One entry per
     thread that needs to do a displaced step.  */
  struct displaced_step_request *step_request_queue;

  /* If this is not null_ptid, this is the thread carrying out a
     displaced single-step in process PID.  This thread's state will
     require fixing up once it has completed its step.  */
  ptid_t step_ptid;

  /* The architecture the thread had when we stepped it.  */
  struct gdbarch *step_gdbarch;

  /* The closure provided gdbarch_displaced_step_copy_insn, to be used
     for post-step cleanup.  */
  struct displaced_step_closure *step_closure;

  /* The address of the original instruction, and the copy we
     made.  */
  CORE_ADDR step_original, step_copy;

  /* Saved contents of copy area.  */
  gdb_byte *step_saved_copy;
};

/* The list of states of processes involved in displaced stepping
   presently.  */
static struct displaced_step_inferior_state *displaced_step_inferior_states;

/* Get the displaced stepping state of process PID.  */

static struct displaced_step_inferior_state *
get_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *state;

  for (state = displaced_step_inferior_states;
       state != NULL;
       state = state->next)
    if (state->pid == pid)
      return state;

  return NULL;
}

/* Add a new displaced stepping state for process PID to the displaced
   stepping state list, or return a pointer to an already existing
   entry, if it already exists.  Never returns NULL.  */

static struct displaced_step_inferior_state *
add_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *state;

  for (state = displaced_step_inferior_states;
       state != NULL;
       state = state->next)
    if (state->pid == pid)
      return state;

  state = xcalloc (1, sizeof (*state));
  state->pid = pid;
  state->next = displaced_step_inferior_states;
  displaced_step_inferior_states = state;

  return state;
}

/* If inferior is in displaced stepping, and ADDR equals to starting address
   of copy area, return corresponding displaced_step_closure.  Otherwise,
   return NULL.  */

struct displaced_step_closure*
get_displaced_step_closure_by_addr (CORE_ADDR addr)
{
  struct displaced_step_inferior_state *displaced
    = get_displaced_stepping_state (ptid_get_pid (inferior_ptid));

  /* If checking the mode of displaced instruction in copy area.  */
  if (displaced && !ptid_equal (displaced->step_ptid, null_ptid)
     && (displaced->step_copy == addr))
    return displaced->step_closure;

  return NULL;
}

/* Remove the displaced stepping state of process PID.  */

static void
remove_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *it, **prev_next_p;

  gdb_assert (pid != 0);

  it = displaced_step_inferior_states;
  prev_next_p = &displaced_step_inferior_states;
  while (it)
    {
      if (it->pid == pid)
	{
	  *prev_next_p = it->next;
	  xfree (it);
	  return;
	}

      prev_next_p = &it->next;
      it = *prev_next_p;
    }
}

static void
infrun_inferior_exit (struct inferior *inf)
{
  remove_displaced_stepping_state (inf->pid);
}

/* If ON, and the architecture supports it, GDB will use displaced
   stepping to step over breakpoints.  If OFF, or if the architecture
   doesn't support it, GDB will instead use the traditional
   hold-and-step approach.  If AUTO (which is the default), GDB will
   decide which technique to use to step over breakpoints depending on
   which of all-stop or non-stop mode is active --- displaced stepping
   in non-stop mode; hold-and-step in all-stop mode.  */

static enum auto_boolean can_use_displaced_stepping = AUTO_BOOLEAN_AUTO;

static void
show_can_use_displaced_stepping (struct ui_file *file, int from_tty,
				 struct cmd_list_element *c,
				 const char *value)
{
  if (can_use_displaced_stepping == AUTO_BOOLEAN_AUTO)
    fprintf_filtered (file,
		      _("Debugger's willingness to use displaced stepping "
			"to step over breakpoints is %s (currently %s).\n"),
		      value, non_stop ? "on" : "off");
  else
    fprintf_filtered (file,
		      _("Debugger's willingness to use displaced stepping "
			"to step over breakpoints is %s.\n"), value);
}

/* Return non-zero if displaced stepping can/should be used to step
   over breakpoints.  */

static int
use_displaced_stepping (struct gdbarch *gdbarch)
{
  return (((can_use_displaced_stepping == AUTO_BOOLEAN_AUTO && non_stop)
	   || can_use_displaced_stepping == AUTO_BOOLEAN_TRUE)
	  && gdbarch_displaced_step_copy_insn_p (gdbarch)
	  && !RECORD_IS_USED);
}

/* Clean out any stray displaced stepping state.  */
static void
displaced_step_clear (struct displaced_step_inferior_state *displaced)
{
  /* Indicate that there is no cleanup pending.  */
  displaced->step_ptid = null_ptid;

  if (displaced->step_closure)
    {
      gdbarch_displaced_step_free_closure (displaced->step_gdbarch,
                                           displaced->step_closure);
      displaced->step_closure = NULL;
    }
}

static void
displaced_step_clear_cleanup (void *arg)
{
  struct displaced_step_inferior_state *state = arg;

  displaced_step_clear (state);
}

/* Dump LEN bytes at BUF in hex to FILE, followed by a newline.  */
void
displaced_step_dump_bytes (struct ui_file *file,
                           const gdb_byte *buf,
                           size_t len)
{
  int i;

  for (i = 0; i < len; i++)
    fprintf_unfiltered (file, "%02x ", buf[i]);
  fputs_unfiltered ("\n", file);
}

/* Prepare to single-step, using displaced stepping.

   Note that we cannot use displaced stepping when we have a signal to
   deliver.  If we have a signal to deliver and an instruction to step
   over, then after the step, there will be no indication from the
   target whether the thread entered a signal handler or ignored the
   signal and stepped over the instruction successfully --- both cases
   result in a simple SIGTRAP.  In the first case we mustn't do a
   fixup, and in the second case we must --- but we can't tell which.
   Comments in the code for 'random signals' in handle_inferior_event
   explain how we handle this case instead.

   Returns 1 if preparing was successful -- this thread is going to be
   stepped now; or 0 if displaced stepping this thread got queued.  */
static int
displaced_step_prepare (ptid_t ptid)
{
  struct cleanup *old_cleanups, *ignore_cleanups;
  struct regcache *regcache = get_thread_regcache (ptid);
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  CORE_ADDR original, copy;
  ULONGEST len;
  struct displaced_step_closure *closure;
  struct displaced_step_inferior_state *displaced;
  int status;

  /* We should never reach this function if the architecture does not
     support displaced stepping.  */
  gdb_assert (gdbarch_displaced_step_copy_insn_p (gdbarch));

  /* We have to displaced step one thread at a time, as we only have
     access to a single scratch space per inferior.  */

  displaced = add_displaced_stepping_state (ptid_get_pid (ptid));

  if (!ptid_equal (displaced->step_ptid, null_ptid))
    {
      /* Already waiting for a displaced step to finish.  Defer this
	 request and place in queue.  */
      struct displaced_step_request *req, *new_req;

      if (debug_displaced)
	fprintf_unfiltered (gdb_stdlog,
			    "displaced: defering step of %s\n",
			    target_pid_to_str (ptid));

      new_req = xmalloc (sizeof (*new_req));
      new_req->ptid = ptid;
      new_req->next = NULL;

      if (displaced->step_request_queue)
	{
	  for (req = displaced->step_request_queue;
	       req && req->next;
	       req = req->next)
	    ;
	  req->next = new_req;
	}
      else
	displaced->step_request_queue = new_req;

      return 0;
    }
  else
    {
      if (debug_displaced)
	fprintf_unfiltered (gdb_stdlog,
			    "displaced: stepping %s now\n",
			    target_pid_to_str (ptid));
    }

  displaced_step_clear (displaced);

  old_cleanups = save_inferior_ptid ();
  inferior_ptid = ptid;

  original = regcache_read_pc (regcache);

  copy = gdbarch_displaced_step_location (gdbarch);
  len = gdbarch_max_insn_length (gdbarch);

  /* Save the original contents of the copy area.  */
  displaced->step_saved_copy = xmalloc (len);
  ignore_cleanups = make_cleanup (free_current_contents,
				  &displaced->step_saved_copy);
  status = target_read_memory (copy, displaced->step_saved_copy, len);
  if (status != 0)
    throw_error (MEMORY_ERROR,
		 _("Error accessing memory address %s (%s) for "
		   "displaced-stepping scratch space."),
		 paddress (gdbarch, copy), safe_strerror (status));
  if (debug_displaced)
    {
      fprintf_unfiltered (gdb_stdlog, "displaced: saved %s: ",
			  paddress (gdbarch, copy));
      displaced_step_dump_bytes (gdb_stdlog,
				 displaced->step_saved_copy,
				 len);
    };

  closure = gdbarch_displaced_step_copy_insn (gdbarch,
					      original, copy, regcache);

  /* We don't support the fully-simulated case at present.  */
  gdb_assert (closure);

  /* Save the information we need to fix things up if the step
     succeeds.  */
  displaced->step_ptid = ptid;
  displaced->step_gdbarch = gdbarch;
  displaced->step_closure = closure;
  displaced->step_original = original;
  displaced->step_copy = copy;

  make_cleanup (displaced_step_clear_cleanup, displaced);

  /* Resume execution at the copy.  */
  regcache_write_pc (regcache, copy);

  discard_cleanups (ignore_cleanups);

  do_cleanups (old_cleanups);

  if (debug_displaced)
    fprintf_unfiltered (gdb_stdlog, "displaced: displaced pc to %s\n",
			paddress (gdbarch, copy));

  return 1;
}

static void
write_memory_ptid (ptid_t ptid, CORE_ADDR memaddr,
		   const gdb_byte *myaddr, int len)
{
  struct cleanup *ptid_cleanup = save_inferior_ptid ();

  inferior_ptid = ptid;
  write_memory (memaddr, myaddr, len);
  do_cleanups (ptid_cleanup);
}

/* Restore the contents of the copy area for thread PTID.  */

static void
displaced_step_restore (struct displaced_step_inferior_state *displaced,
			ptid_t ptid)
{
  ULONGEST len = gdbarch_max_insn_length (displaced->step_gdbarch);

  write_memory_ptid (ptid, displaced->step_copy,
		     displaced->step_saved_copy, len);
  if (debug_displaced)
    fprintf_unfiltered (gdb_stdlog, "displaced: restored %s %s\n",
			target_pid_to_str (ptid),
			paddress (displaced->step_gdbarch,
				  displaced->step_copy));
}

static void
displaced_step_fixup (ptid_t event_ptid, enum gdb_signal signal)
{
  struct cleanup *old_cleanups;
  struct displaced_step_inferior_state *displaced
    = get_displaced_stepping_state (ptid_get_pid (event_ptid));

  /* Was any thread of this process doing a displaced step?  */
  if (displaced == NULL)
    return;

  /* Was this event for the pid we displaced?  */
  if (ptid_equal (displaced->step_ptid, null_ptid)
      || ! ptid_equal (displaced->step_ptid, event_ptid))
    return;

  old_cleanups = make_cleanup (displaced_step_clear_cleanup, displaced);

  displaced_step_restore (displaced, displaced->step_ptid);

  /* Did the instruction complete successfully?  */
  if (signal == GDB_SIGNAL_TRAP)
    {
      /* Fix up the resulting state.  */
      gdbarch_displaced_step_fixup (displaced->step_gdbarch,
                                    displaced->step_closure,
                                    displaced->step_original,
                                    displaced->step_copy,
                                    get_thread_regcache (displaced->step_ptid));
    }
  else
    {
      /* Since the instruction didn't complete, all we can do is
         relocate the PC.  */
      struct regcache *regcache = get_thread_regcache (event_ptid);
      CORE_ADDR pc = regcache_read_pc (regcache);

      pc = displaced->step_original + (pc - displaced->step_copy);
      regcache_write_pc (regcache, pc);
    }

  do_cleanups (old_cleanups);

  displaced->step_ptid = null_ptid;

  /* Are there any pending displaced stepping requests?  If so, run
     one now.  Leave the state object around, since we're likely to
     need it again soon.  */
  while (displaced->step_request_queue)
    {
      struct displaced_step_request *head;
      ptid_t ptid;
      struct regcache *regcache;
      struct gdbarch *gdbarch;
      CORE_ADDR actual_pc;
      struct address_space *aspace;

      head = displaced->step_request_queue;
      ptid = head->ptid;
      displaced->step_request_queue = head->next;
      xfree (head);

      context_switch (ptid);

      regcache = get_thread_regcache (ptid);
      actual_pc = regcache_read_pc (regcache);
      aspace = get_regcache_aspace (regcache);

      if (breakpoint_here_p (aspace, actual_pc))
	{
	  if (debug_displaced)
	    fprintf_unfiltered (gdb_stdlog,
				"displaced: stepping queued %s now\n",
				target_pid_to_str (ptid));

	  displaced_step_prepare (ptid);

	  gdbarch = get_regcache_arch (regcache);

	  if (debug_displaced)
	    {
	      CORE_ADDR actual_pc = regcache_read_pc (regcache);
	      gdb_byte buf[4];

	      fprintf_unfiltered (gdb_stdlog, "displaced: run %s: ",
				  paddress (gdbarch, actual_pc));
	      read_memory (actual_pc, buf, sizeof (buf));
	      displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
	    }

	  if (gdbarch_displaced_step_hw_singlestep (gdbarch,
						    displaced->step_closure))
	    target_resume (ptid, 1, GDB_SIGNAL_0);
	  else
	    target_resume (ptid, 0, GDB_SIGNAL_0);

	  /* Done, we're stepping a thread.  */
	  break;
	}
      else
	{
	  int step;
	  struct thread_info *tp = inferior_thread ();

	  /* The breakpoint we were sitting under has since been
	     removed.  */
	  tp->control.trap_expected = 0;

	  /* Go back to what we were trying to do.  */
	  step = currently_stepping (tp);

	  if (debug_displaced)
	    fprintf_unfiltered (gdb_stdlog,
				"displaced: breakpoint is gone: %s, step(%d)\n",
				target_pid_to_str (tp->ptid), step);

	  target_resume (ptid, step, GDB_SIGNAL_0);
	  tp->suspend.stop_signal = GDB_SIGNAL_0;

	  /* This request was discarded.  See if there's any other
	     thread waiting for its turn.  */
	}
    }
}

/* Update global variables holding ptids to hold NEW_PTID if they were
   holding OLD_PTID.  */
static void
infrun_thread_ptid_changed (ptid_t old_ptid, ptid_t new_ptid)
{
  struct displaced_step_request *it;
  struct displaced_step_inferior_state *displaced;

  if (ptid_equal (inferior_ptid, old_ptid))
    inferior_ptid = new_ptid;

  if (ptid_equal (singlestep_ptid, old_ptid))
    singlestep_ptid = new_ptid;

  if (ptid_equal (deferred_step_ptid, old_ptid))
    deferred_step_ptid = new_ptid;

  for (displaced = displaced_step_inferior_states;
       displaced;
       displaced = displaced->next)
    {
      if (ptid_equal (displaced->step_ptid, old_ptid))
	displaced->step_ptid = new_ptid;

      for (it = displaced->step_request_queue; it; it = it->next)
	if (ptid_equal (it->ptid, old_ptid))
	  it->ptid = new_ptid;
    }
}


/* Resuming.  */

/* Things to clean up if we QUIT out of resume ().  */
static void
resume_cleanups (void *ignore)
{
  normal_stop ();
}

static const char schedlock_off[] = "off";
static const char schedlock_on[] = "on";
static const char schedlock_step[] = "step";
static const char *const scheduler_enums[] = {
  schedlock_off,
  schedlock_on,
  schedlock_step,
  NULL
};
static const char *scheduler_mode = schedlock_off;
static void
show_scheduler_mode (struct ui_file *file, int from_tty,
		     struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
		    _("Mode for locking scheduler "
		      "during execution is \"%s\".\n"),
		    value);
}

static void
set_schedlock_func (char *args, int from_tty, struct cmd_list_element *c)
{
  if (!target_can_lock_scheduler)
    {
      scheduler_mode = schedlock_off;
      error (_("Target '%s' cannot support this command."), target_shortname);
    }
}

/* True if execution commands resume all threads of all processes by
   default; otherwise, resume only threads of the current inferior
   process.  */
int sched_multi = 0;

/* Try to setup for software single stepping over the specified location.
   Return 1 if target_resume() should use hardware single step.

   GDBARCH the current gdbarch.
   PC the location to step over.  */

static int
maybe_software_singlestep (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  int hw_step = 1;

  if (execution_direction == EXEC_FORWARD
      && gdbarch_software_single_step_p (gdbarch)
      && gdbarch_software_single_step (gdbarch, get_current_frame ()))
    {
      hw_step = 0;
      /* Do not pull these breakpoints until after a `wait' in
	 `wait_for_inferior'.  */
      singlestep_breakpoints_inserted_p = 1;
      singlestep_ptid = inferior_ptid;
      singlestep_pc = pc;
    }
  return hw_step;
}

/* Return a ptid representing the set of threads that we will proceed,
   in the perspective of the user/frontend.  We may actually resume
   fewer threads at first, e.g., if a thread is stopped at a
   breakpoint that needs stepping-off, but that should not be visible
   to the user/frontend, and neither should the frontend/user be
   allowed to proceed any of the threads that happen to be stopped for
   internal run control handling, if a previous command wanted them
   resumed.  */

ptid_t
user_visible_resume_ptid (int step)
{
  /* By default, resume all threads of all processes.  */
  ptid_t resume_ptid = RESUME_ALL;

  /* Maybe resume only all threads of the current process.  */
  if (!sched_multi && target_supports_multi_process ())
    {
      resume_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
    }

  /* Maybe resume a single thread after all.  */
  if (non_stop)
    {
      /* With non-stop mode on, threads are always handled
	 individually.  */
      resume_ptid = inferior_ptid;
    }
  else if ((scheduler_mode == schedlock_on)
	   || (scheduler_mode == schedlock_step
	       && (step || singlestep_breakpoints_inserted_p)))
    {
      /* User-settable 'scheduler' mode requires solo thread resume.  */
      resume_ptid = inferior_ptid;
    }

  return resume_ptid;
}

/* Resume the inferior, but allow a QUIT.  This is useful if the user
   wants to interrupt some lengthy single-stepping operation
   (for child processes, the SIGINT goes to the inferior, and so
   we get a SIGINT random_signal, but for remote debugging and perhaps
   other targets, that's not true).

   STEP nonzero if we should step (zero to continue instead).
   SIG is the signal to give the inferior (zero for none).  */
void
resume (int step, enum gdb_signal sig)
{
  int should_resume = 1;
  struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
  struct regcache *regcache = get_current_regcache ();
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  struct thread_info *tp = inferior_thread ();
  CORE_ADDR pc = regcache_read_pc (regcache);
  struct address_space *aspace = get_regcache_aspace (regcache);

  QUIT;

  if (current_inferior ()->waiting_for_vfork_done)
    {
      /* Don't try to single-step a vfork parent that is waiting for
	 the child to get out of the shared memory region (by exec'ing
	 or exiting).  This is particularly important on software
	 single-step archs, as the child process would trip on the
	 software single step breakpoint inserted for the parent
	 process.  Since the parent will not actually execute any
	 instruction until the child is out of the shared region (such
	 are vfork's semantics), it is safe to simply continue it.
	 Eventually, we'll see a TARGET_WAITKIND_VFORK_DONE event for
	 the parent, and tell it to `keep_going', which automatically
	 re-sets it stepping.  */
      if (debug_infrun)
	fprintf_unfiltered (gdb_stdlog,
			    "infrun: resume : clear step\n");
      step = 0;
    }

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: resume (step=%d, signal=%d), "
			"trap_expected=%d, current thread [%s] at %s\n",
 			step, sig, tp->control.trap_expected,
			target_pid_to_str (inferior_ptid),
			paddress (gdbarch, pc));

  /* Normally, by the time we reach `resume', the breakpoints are either
     removed or inserted, as appropriate.  The exception is if we're sitting
     at a permanent breakpoint; we need to step over it, but permanent
     breakpoints can't be removed.  So we have to test for it here.  */
  if (breakpoint_here_p (aspace, pc) == permanent_breakpoint_here)
    {
      if (gdbarch_skip_permanent_breakpoint_p (gdbarch))
	gdbarch_skip_permanent_breakpoint (gdbarch, regcache);
      else
	error (_("\
The program is stopped at a permanent breakpoint, but GDB does not know\n\
how to step past a permanent breakpoint on this architecture.  Try using\n\
a command like `return' or `jump' to continue execution."));
    }

  /* If enabled, step over breakpoints by executing a copy of the
     instruction at a different address.

     We can't use displaced stepping when we have a signal to deliver;
     the comments for displaced_step_prepare explain why.  The
     comments in the handle_inferior event for dealing with 'random
     signals' explain what we do instead.

     We can't use displaced stepping when we are waiting for vfork_done
     event, displaced stepping breaks the vfork child similarly as single
     step software breakpoint.  */
  if (use_displaced_stepping (gdbarch)
      && (tp->control.trap_expected
	  || (step && gdbarch_software_single_step_p (gdbarch)))
      && sig == GDB_SIGNAL_0
      && !current_inferior ()->waiting_for_vfork_done)
    {
      struct displaced_step_inferior_state *displaced;

      if (!displaced_step_prepare (inferior_ptid))
	{
	  /* Got placed in displaced stepping queue.  Will be resumed
	     later when all the currently queued displaced stepping
	     requests finish.  The thread is not executing at this point,
	     and the call to set_executing will be made later.  But we
	     need to call set_running here, since from frontend point of view,
	     the thread is running.  */
	  set_running (inferior_ptid, 1);
	  discard_cleanups (old_cleanups);
	  return;
	}

      /* Update pc to reflect the new address from which we will execute
	 instructions due to displaced stepping.  */
      pc = regcache_read_pc (get_thread_regcache (inferior_ptid));

      displaced = get_displaced_stepping_state (ptid_get_pid (inferior_ptid));
      step = gdbarch_displaced_step_hw_singlestep (gdbarch,
						   displaced->step_closure);
    }

  /* Do we need to do it the hard way, w/temp breakpoints?  */
  else if (step)
    step = maybe_software_singlestep (gdbarch, pc);

  /* Currently, our software single-step implementation leads to different
     results than hardware single-stepping in one situation: when stepping
     into delivering a signal which has an associated signal handler,
     hardware single-step will stop at the first instruction of the handler,
     while software single-step will simply skip execution of the handler.

     For now, this difference in behavior is accepted since there is no
     easy way to actually implement single-stepping into a signal handler
     without kernel support.

     However, there is one scenario where this difference leads to follow-on
     problems: if we're stepping off a breakpoint by removing all breakpoints
     and then single-stepping.  In this case, the software single-step
     behavior means that even if there is a *breakpoint* in the signal
     handler, GDB still would not stop.

     Fortunately, we can at least fix this particular issue.  We detect
     here the case where we are about to deliver a signal while software
     single-stepping with breakpoints removed.  In this situation, we
     revert the decisions to remove all breakpoints and insert single-
     step breakpoints, and instead we install a step-resume breakpoint
     at the current address, deliver the signal without stepping, and
     once we arrive back at the step-resume breakpoint, actually step
     over the breakpoint we originally wanted to step over.  */
  if (singlestep_breakpoints_inserted_p
      && tp->control.trap_expected && sig != GDB_SIGNAL_0)
    {
      /* If we have nested signals or a pending signal is delivered
	 immediately after a handler returns, might might already have
	 a step-resume breakpoint set on the earlier handler.  We cannot
	 set another step-resume breakpoint; just continue on until the
	 original breakpoint is hit.  */
      if (tp->control.step_resume_breakpoint == NULL)
	{
	  insert_hp_step_resume_breakpoint_at_frame (get_current_frame ());
	  tp->step_after_step_resume_breakpoint = 1;
	}

      remove_single_step_breakpoints ();
      singlestep_breakpoints_inserted_p = 0;

      insert_breakpoints ();
      tp->control.trap_expected = 0;
    }

  if (should_resume)
    {
      ptid_t resume_ptid;

      /* If STEP is set, it's a request to use hardware stepping
	 facilities.  But in that case, we should never
	 use singlestep breakpoint.  */
      gdb_assert (!(singlestep_breakpoints_inserted_p && step));

      /* Decide the set of threads to ask the target to resume.  Start
	 by assuming everything will be resumed, than narrow the set
	 by applying increasingly restricting conditions.  */
      resume_ptid = user_visible_resume_ptid (step);

      /* Maybe resume a single thread after all.  */
      if (singlestep_breakpoints_inserted_p
	  && stepping_past_singlestep_breakpoint)
	{
	  /* The situation here is as follows.  In thread T1 we wanted to
	     single-step.  Lacking hardware single-stepping we've
	     set breakpoint at the PC of the next instruction -- call it
	     P.  After resuming, we've hit that breakpoint in thread T2.
	     Now we've removed original breakpoint, inserted breakpoint
	     at P+1, and try to step to advance T2 past breakpoint.
	     We need to step only T2, as if T1 is allowed to freely run,
	     it can run past P, and if other threads are allowed to run,
	     they can hit breakpoint at P+1, and nested hits of single-step
	     breakpoints is not something we'd want -- that's complicated
	     to support, and has no value.  */
	  resume_ptid = inferior_ptid;
	}
      else if ((step || singlestep_breakpoints_inserted_p)
	       && tp->control.trap_expected)
	{
	  /* We're allowing a thread to run past a breakpoint it has
	     hit, by single-stepping the thread with the breakpoint
	     removed.  In which case, we need to single-step only this
	     thread, and keep others stopped, as they can miss this
	     breakpoint if allowed to run.

	     The current code actually removes all breakpoints when
	     doing this, not just the one being stepped over, so if we
	     let other threads run, we can actually miss any
	     breakpoint, not just the one at PC.  */
	  resume_ptid = inferior_ptid;
	}

      if (gdbarch_cannot_step_breakpoint (gdbarch))
	{
	  /* Most targets can step a breakpoint instruction, thus
	     executing it normally.  But if this one cannot, just
	     continue and we will hit it anyway.  */
	  if (step && breakpoint_inserted_here_p (aspace, pc))
	    step = 0;
	}

      if (debug_displaced
          && use_displaced_stepping (gdbarch)
          && tp->control.trap_expected)
        {
	  struct regcache *resume_regcache = get_thread_regcache (resume_ptid);
	  struct gdbarch *resume_gdbarch = get_regcache_arch (resume_regcache);
          CORE_ADDR actual_pc = regcache_read_pc (resume_regcache);
          gdb_byte buf[4];

          fprintf_unfiltered (gdb_stdlog, "displaced: run %s: ",
                              paddress (resume_gdbarch, actual_pc));
          read_memory (actual_pc, buf, sizeof (buf));
          displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
        }

      /* Install inferior's terminal modes.  */
      target_terminal_inferior ();

      /* Avoid confusing the next resume, if the next stop/resume
	 happens to apply to another thread.  */
      tp->suspend.stop_signal = GDB_SIGNAL_0;

      /* Advise target which signals may be handled silently.  If we have
	 removed breakpoints because we are stepping over one (which can
	 happen only if we are not using displaced stepping), we need to
	 receive all signals to avoid accidentally skipping a breakpoint
	 during execution of a signal handler.  */
      if ((step || singlestep_breakpoints_inserted_p)
	  && tp->control.trap_expected
	  && !use_displaced_stepping (gdbarch))
	target_pass_signals (0, NULL);
      else
	target_pass_signals ((int) GDB_SIGNAL_LAST, signal_pass);

      target_resume (resume_ptid, step, sig);
    }

  discard_cleanups (old_cleanups);
}

/* Proceeding.  */

/* Clear out all variables saying what to do when inferior is continued.
   First do this, then set the ones you want, then call `proceed'.  */

static void
clear_proceed_status_thread (struct thread_info *tp)
{
  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
			"infrun: clear_proceed_status_thread (%s)\n",
			target_pid_to_str (tp->ptid));

  tp->control.trap_expected = 0;
  tp->control.step_range_start = 0;
  tp->control.step_range_end = 0;
  tp->control.step_frame_id = null_frame_id;
  tp->control.step_stack_frame_id = null_frame_id;
  tp->control.step_over_calls = STEP_OVER_UNDEBUGGABLE;
  tp->stop_requested = 0;

  tp->control.stop_step = 0;

  tp->control.proceed_to_finish = 0;

  /* Discard any remaining commands or status from previous stop.  */
  bpstat_clear (&tp->control.stop_bpstat);
}

static int
clear_proceed_status_callback (struct thread_info *tp, void *data)
{
  if (is_exited (tp->ptid))
    return 0;

  clear_proceed_status_thread (tp);
  return 0;
}

void
clear_proceed_status (void)
{
  if (!non_stop)
    {
      /* In all-stop mode, delete the per-thread status of all
	 threads, even if inferior_ptid is null_ptid, there may be
	 threads on the list.  E.g., we may be launching a new
	 process, while selecting the executable.  */
      iterate_over_threads (clear_proceed_status_callback, NULL);
    }

  if (!ptid_equal (inferior_ptid, null_ptid))
    {
      struct inferior *inferior;

      if (non_stop)
	{
	  /* If in non-stop mode, only delete the per-thread status of
	     the current thread.  */
	  clear_proceed_status_thread (inferior_thread ());
	}

      inferior = current_inferior ();
      inferior->control.stop_soon = NO_STOP_QUIETLY;
    }

  stop_after_trap = 0;

  observer_notify_about_to_proceed ();

  if (stop_registers)
    {
      regcache_xfree (stop_registers);
      stop_registers = NULL;
    }
}

/* Check the current thread against the thread that reported the most recent
   event.  If a step-over is required return TRUE and set the current thread
   to the old thread.  Otherwise return FALSE.

   This should be suitable for any targets that support threads.  */

static int
prepare_to_proceed (int step)
{
  ptid_t wait_ptid;
  struct target_waitstatus wait_status;
  int schedlock_enabled;

  /* With non-stop mode on, threads are always handled individually.  */
  gdb_assert (! non_stop);

  /* Get the last target status returned by target_wait().  */
  get_last_target_status (&wait_ptid, &wait_status);

  /* Make sure we were stopped at a breakpoint.  */
  if (wait_status.kind != TARGET_WAITKIND_STOPPED
      || (wait_status.value.sig != GDB_SIGNAL_TRAP
	  && wait_status.value.sig != GDB_SIGNAL_ILL
	  && wait_status.value.sig != GDB_SIGNAL_SEGV
	  && wait_status.value.sig != GDB_SIGNAL_EMT))
    {
      return 0;
    }

  schedlock_enabled = (scheduler_mode == schedlock_on
		       || (scheduler_mode == schedlock_step
			   && step));

  /* Don't switch over to WAIT_PTID if scheduler locking is on.  */
  if (schedlock_enabled)
    return 0;

  /* Don't switch over if we're about to resume some other process
     other than WAIT_PTID's, and schedule-multiple is off.  */
  if (!sched_multi
      && ptid_get_pid (wait_ptid) != ptid_get_pid (inferior_ptid))
    return 0;

  /* Switched over from WAIT_PID.  */
  if (!ptid_equal (wait_ptid, minus_one_ptid)
      && !ptid_equal (inferior_ptid, wait_ptid))
    {
      struct regcache *regcache = get_thread_regcache (wait_ptid);

      if (breakpoint_here_p (get_regcache_aspace (regcache),
			     regcache_read_pc (regcache)))
	{
	  /* If stepping, remember current thread to switch back to.  */
	  if (step)
	    deferred_step_ptid = inferior_ptid;

	  /* Switch back to WAIT_PID thread.  */
	  switch_to_thread (wait_ptid);

	  if (debug_infrun)
	    fprintf_unfiltered (gdb_stdlog,
				"infrun: prepare_to_proceed (step=%d), "
				"switched to [%s]\n",
				step, target_pid_to_str (inferior_ptid));

	  /* We return 1 to indicate that there is a breakpoint here,
	     so we need to step over it before continuing to avoid
	     hitting it straight away.  */
	  return 1;
	}
    }

  return 0;
}

/* Basic routine for continuing the program in various fashions.

   ADDR is the address to resume at, or -1 for resume where stopped.
   SIGGNAL is the signal to give it, or 0 for none,
   or -1 for act according to how it stopped.
   STEP is nonzero if should trap after one instruction.
   -1 means return after that and print nothing.
   You should probably set various step_... variables
   before calling here, if you are stepping.

   You should call clear_proceed_status before calling proceed.  */

void
proceed (CORE_ADDR addr, enum gdb_signal siggnal, int step)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  struct thread_info *tp;
  CORE_ADDR pc;
  struct address_space *aspace;
  int oneproc = 0;

  /* If we're stopped at a fork/vfork, follow the branch set by the
     "set follow-fork-mode" command; otherwise, we'll just proceed
     resuming the current thread.  */
  if (!follow_fork ())
    {
      /* The target for some reason decided not to resume.  */
      normal_stop ();
      if (target_can_async_p ())
	inferior_event_handler (INF_EXEC_COMPLETE, NULL);
      return;
    }

  /* We'll update this if & when we switch to a new thread.  */
  previous_inferior_ptid = inferior_ptid;

  regcache = get_current_regcache ();
  gdbarch = get_regcache_arch (regcache);
  aspace = get_regcache_aspace (regcache);
  pc = regcache_read_pc (regcache);

  if (step > 0)
    step_start_function = find_pc_function (pc);
  if (step < 0)
    stop_after_trap = 1;

  if (addr == (CORE_ADDR) -1)
    {
      if (pc == stop_pc && breakpoint_here_p (aspace, pc)
	  && execution_direction != EXEC_REVERSE)
	/* There is a breakpoint at the address we will resume at,
	   step one instruction before inserting breakpoints so that
	   we do not stop right away (and report a second hit at this
	   breakpoint).

	   Note, we don't do this in reverse, because we won't
	   actually be executing the breakpoint insn anyway.
	   We'll be (un-)executing the previous instruction.  */

	oneproc = 1;
      else if (gdbarch_single_step_through_delay_p (gdbarch)
	       && gdbarch_single_step_through_delay (gdbarch,
						     get_current_frame ()))
	/* We stepped onto an instruction that needs to be stepped
	   again before re-inserting the breakpoint, do so.  */
	oneproc = 1;
    }
  else
    {
      regcache_write_pc (regcache, addr);
    }

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
			"infrun: proceed (addr=%s, signal=%d, step=%d)\n",
			paddress (gdbarch, addr), siggnal, step);

  if (non_stop)
    /* In non-stop, each thread is handled individually.  The context
       must already be set to the right thread here.  */
    ;
  else
    {
      /* In a multi-threaded task we may select another thread and
	 then continue or step.

	 But if the old thread was stopped at a breakpoint, it will
	 immediately cause another breakpoint stop without any
	 execution (i.e. it will report a breakpoint hit incorrectly).
	 So we must step over it first.

	 prepare_to_proceed checks the current thread against the
	 thread that reported the most recent event.  If a step-over
	 is required it returns TRUE and sets the current thread to
	 the old thread.  */
      if (prepare_to_proceed (step))
	oneproc = 1;
    }

  /* prepare_to_proceed may change the current thread.  */
  tp = inferior_thread ();

  if (oneproc)
    {
      tp->control.trap_expected = 1;
      /* If displaced stepping is enabled, we can step over the
	 breakpoint without hitting it, so leave all breakpoints
	 inserted.  Otherwise we need to disable all breakpoints, step
	 one instruction, and then re-add them when that step is
	 finished.  */
      if (!use_displaced_stepping (gdbarch))
	remove_breakpoints ();
    }

  /* We can insert breakpoints if we're not trying to step over one,
     or if we are stepping over one but we're using displaced stepping
     to do so.  */
  if (! tp->control.trap_expected || use_displaced_stepping (gdbarch))
    insert_breakpoints ();

  if (!non_stop)
    {
      /* Pass the last stop signal to the thread we're resuming,
	 irrespective of whether the current thread is the thread that
	 got the last event or not.  This was historically GDB's
	 behaviour before keeping a stop_signal per thread.  */

      struct thread_info *last_thread;
      ptid_t last_ptid;
      struct target_waitstatus last_status;

      get_last_target_status (&last_ptid, &last_status);
      if (!ptid_equal (inferior_ptid, last_ptid)
	  && !ptid_equal (last_ptid, null_ptid)
	  && !ptid_equal (last_ptid, minus_one_ptid))
	{
	  last_thread = find_thread_ptid (last_ptid);
	  if (last_thread)
	    {
	      tp->suspend.stop_signal = last_thread->suspend.stop_signal;
	      last_thread->suspend.stop_signal = GDB_SIGNAL_0;
	    }
	}
    }

  if (siggnal != GDB_SIGNAL_DEFAULT)
    tp->suspend.stop_signal = siggnal;
  /* If this signal should not be seen by program,
     give it zero.  Used for debugging signals.  */
  else if (!signal_program[tp->suspend.stop_signal])
    tp->suspend.stop_signal = GDB_SIGNAL_0;

  annotate_starting ();

  /* Make sure that output from GDB appears before output from the
     inferior.  */
  gdb_flush (gdb_stdout);

  /* Refresh prev_pc value just prior to resuming.  This used to be
     done in stop_stepping, however, setting prev_pc there did not handle
     scenarios such as inferior function calls or returning from
     a function via the return command.  In those cases, the prev_pc
     value was not set properly for subsequent commands.  The prev_pc value 
     is used to initialize the starting line number in the ecs.  With an 
     invalid value, the gdb next command ends up stopping at the position
     represented by the next line table entry past our start position.
     On platforms that generate one line table entry per line, this
     is not a problem.  However, on the ia64, the compiler generates
     extraneous line table entries that do not increase the line number.
     When we issue the gdb next command on the ia64 after an inferior call
     or a return command, we often end up a few instructions forward, still 
     within the original line we started.

     An attempt was made to refresh the prev_pc at the same time the
     execution_control_state is initialized (for instance, just before
     waiting for an inferior event).  But this approach did not work
     because of platforms that use ptrace, where the pc register cannot
     be read unless the inferior is stopped.  At that point, we are not
     guaranteed the inferior is stopped and so the regcache_read_pc() call
     can fail.  Setting the prev_pc value here ensures the value is updated
     correctly when the inferior is stopped.  */
  tp->prev_pc = regcache_read_pc (get_current_regcache ());

  /* Fill in with reasonable starting values.  */
  init_thread_stepping_state (tp);

  /* Reset to normal state.  */
  init_infwait_state ();

  /* Resume inferior.  */
  resume (oneproc || step || bpstat_should_step (), tp->suspend.stop_signal);

  /* Wait for it to stop (if not standalone)
     and in any case decode why it stopped, and act accordingly.  */
  /* Do this only if we are not using the event loop, or if the target
     does not support asynchronous execution.  */
  if (!target_can_async_p ())
    {
      wait_for_inferior ();
      normal_stop ();
    }
}


/* Start remote-debugging of a machine over a serial link.  */

void
start_remote (int from_tty)
{
  struct inferior *inferior;

  inferior = current_inferior ();
  inferior->control.stop_soon = STOP_QUIETLY_REMOTE;

  /* Always go on waiting for the target, regardless of the mode.  */
  /* FIXME: cagney/1999-09-23: At present it isn't possible to
     indicate to wait_for_inferior that a target should timeout if
     nothing is returned (instead of just blocking).  Because of this,
     targets expecting an immediate response need to, internally, set
     things up so that the target_wait() is forced to eventually
     timeout.  */
  /* FIXME: cagney/1999-09-24: It isn't possible for target_open() to
     differentiate to its caller what the state of the target is after
     the initial open has been performed.  Here we're assuming that
     the target has stopped.  It should be possible to eventually have
     target_open() return to the caller an indication that the target
     is currently running and GDB state should be set to the same as
     for an async run.  */
  wait_for_inferior ();

  /* Now that the inferior has stopped, do any bookkeeping like
     loading shared libraries.  We want to do this before normal_stop,
     so that the displayed frame is up to date.  */
  post_create_inferior (&current_target, from_tty);

  normal_stop ();
}

/* Initialize static vars when a new inferior begins.  */

void
init_wait_for_inferior (void)
{
  /* These are meaningless until the first time through wait_for_inferior.  */

  breakpoint_init_inferior (inf_starting);

  clear_proceed_status ();

  stepping_past_singlestep_breakpoint = 0;
  deferred_step_ptid = null_ptid;

  target_last_wait_ptid = minus_one_ptid;

  previous_inferior_ptid = inferior_ptid;
  init_infwait_state ();

  /* Discard any skipped inlined frames.  */
  clear_inline_frame_state (minus_one_ptid);
}


/* This enum encodes possible reasons for doing a target_wait, so that
   wfi can call target_wait in one place.  (Ultimately the call will be
   moved out of the infinite loop entirely.) */

enum infwait_states
{
  infwait_normal_state,
  infwait_thread_hop_state,
  infwait_step_watch_state,
  infwait_nonstep_watch_state
};

/* The PTID we'll do a target_wait on.*/
ptid_t waiton_ptid;

/* Current inferior wait state.  */
enum infwait_states infwait_state;

/* Data to be passed around while handling an event.  This data is
   discarded between events.  */
struct execution_control_state
{
  ptid_t ptid;
  /* The thread that got the event, if this was a thread event; NULL
     otherwise.  */
  struct thread_info *event_thread;

  struct target_waitstatus ws;
  int random_signal;
  int stop_func_filled_in;
  CORE_ADDR stop_func_start;
  CORE_ADDR stop_func_end;
  const char *stop_func_name;
  int wait_some_more;
};

static void handle_inferior_event (struct execution_control_state *ecs);

static void handle_step_into_function (struct gdbarch *gdbarch,
				       struct execution_control_state *ecs);
static void handle_step_into_function_backward (struct gdbarch *gdbarch,
						struct execution_control_state *ecs);
static void check_exception_resume (struct execution_control_state *,
				    struct frame_info *);

static void stop_stepping (struct execution_control_state *ecs);
static void prepare_to_wait (struct execution_control_state *ecs);
static void keep_going (struct execution_control_state *ecs);

/* Callback for iterate over threads.  If the thread is stopped, but
   the user/frontend doesn't know about that yet, go through
   normal_stop, as if the thread had just stopped now.  ARG points at
   a ptid.  If PTID is MINUS_ONE_PTID, applies to all threads.  If
   ptid_is_pid(PTID) is true, applies to all threads of the process
   pointed at by PTID.  Otherwise, apply only to the thread pointed by
   PTID.  */

static int
infrun_thread_stop_requested_callback (struct thread_info *info, void *arg)
{
  ptid_t ptid = * (ptid_t *) arg;

  if ((ptid_equal (info->ptid, ptid)
       || ptid_equal (minus_one_ptid, ptid)
       || (ptid_is_pid (ptid)
	   && ptid_get_pid (ptid) == ptid_get_pid (info->ptid)))
      && is_running (info->ptid)
      && !is_executing (info->ptid))
    {
      struct cleanup *old_chain;
      struct execution_control_state ecss;
      struct execution_control_state *ecs = &ecss;

      memset (ecs, 0, sizeof (*ecs));

      old_chain = make_cleanup_restore_current_thread ();

      /* Go through handle_inferior_event/normal_stop, so we always
	 have consistent output as if the stop event had been
	 reported.  */
      ecs->ptid = info->ptid;
      ecs->event_thread = find_thread_ptid (info->ptid);
      ecs->ws.kind = TARGET_WAITKIND_STOPPED;
      ecs->ws.value.sig = GDB_SIGNAL_0;

      handle_inferior_event (ecs);

      if (!ecs->wait_some_more)
	{
	  struct thread_info *tp;

	  normal_stop ();

	  /* Finish off the continuations.  */
	  tp = inferior_thread ();
	  do_all_intermediate_continuations_thread (tp, 1);
	  do_all_continuations_thread (tp, 1);
	}

      do_cleanups (old_chain);
    }

  return 0;
}

/* This function is attached as a "thread_stop_requested" observer.
   Cleanup local state that assumed the PTID was to be resumed, and
   report the stop to the frontend.  */

static void
infrun_thread_stop_requested (ptid_t ptid)
{
  struct displaced_step_inferior_state *displaced;

  /* PTID was requested to stop.  Remove it from the displaced
     stepping queue, so we don't try to resume it automatically.  */

  for (displaced = displaced_step_inferior_states;
       displaced;
       displaced = displaced->next)
    {
      struct displaced_step_request *it, **prev_next_p;

      it = displaced->step_request_queue;
      prev_next_p = &displaced->step_request_queue;
      while (it)
	{
	  if (ptid_match (it->ptid, ptid))
	    {
	      *prev_next_p = it->next;
	      it->next = NULL;
	      xfree (it);
	    }
	  else
	    {
	      prev_next_p = &it->next;
	    }

	  it = *prev_next_p;
	}
    }

  iterate_over_threads (infrun_thread_stop_requested_callback, &ptid);
}

static void
infrun_thread_thread_exit (struct thread_info *tp, int silent)
{
  if (ptid_equal (target_last_wait_ptid, tp->ptid))
    nullify_last_target_wait_ptid ();
}

/* Callback for iterate_over_threads.  */

static int
delete_step_resume_breakpoint_callback (struct thread_info *info, void *data)
{
  if (is_exited (info->ptid))
    return 0;

  delete_step_resume_breakpoint (info);
  delete_exception_resume_breakpoint (info);
  return 0;
}

/* In all-stop, delete the step resume breakpoint of any thread that
   had one.  In non-stop, delete the step resume breakpoint of the
   thread that just stopped.  */

static void
delete_step_thread_step_resume_breakpoint (void)
{
  if (!target_has_execution
      || ptid_equal (inferior_ptid, null_ptid))
    /* If the inferior has exited, we have already deleted the step
       resume breakpoints out of GDB's lists.  */
    return;

  if (non_stop)
    {
      /* If in non-stop mode, only delete the step-resume or
	 longjmp-resume breakpoint of the thread that just stopped
	 stepping.  */
      struct thread_info *tp = inferior_thread ();

      delete_step_resume_breakpoint (tp);
      delete_exception_resume_breakpoint (tp);
    }
  else
    /* In all-stop mode, delete all step-resume and longjmp-resume
       breakpoints of any thread that had them.  */
    iterate_over_threads (delete_step_resume_breakpoint_callback, NULL);
}

/* A cleanup wrapper.  */

static void
delete_step_thread_step_resume_breakpoint_cleanup (void *arg)
{
  delete_step_thread_step_resume_breakpoint ();
}

/* Pretty print the results of target_wait, for debugging purposes.  */

static void
print_target_wait_results (ptid_t waiton_ptid, ptid_t result_ptid,
			   const struct target_waitstatus *ws)
{
  char *status_string = target_waitstatus_to_string (ws);
  struct ui_file *tmp_stream = mem_fileopen ();
  char *text;

  /* The text is split over several lines because it was getting too long.
     Call fprintf_unfiltered (gdb_stdlog) once so that the text is still
     output as a unit; we want only one timestamp printed if debug_timestamp
     is set.  */

  fprintf_unfiltered (tmp_stream,
		      "infrun: target_wait (%d", PIDGET (waiton_ptid));
  if (PIDGET (waiton_ptid) != -1)
    fprintf_unfiltered (tmp_stream,
			" [%s]", target_pid_to_str (waiton_ptid));
  fprintf_unfiltered (tmp_stream, ", status) =\n");
  fprintf_unfiltered (tmp_stream,
		      "infrun:   %d [%s],\n",
		      PIDGET (result_ptid), target_pid_to_str (result_ptid));
  fprintf_unfiltered (tmp_stream,
		      "infrun:   %s\n",
		      status_string);

  text = ui_file_xstrdup (tmp_stream, NULL);

  /* This uses %s in part to handle %'s in the text, but also to avoid
     a gcc error: the format attribute requires a string literal.  */
  fprintf_unfiltered (gdb_stdlog, "%s", text);

  xfree (status_string);
  xfree (text);
  ui_file_delete (tmp_stream);
}

/* Prepare and stabilize the inferior for detaching it.  E.g.,
   detaching while a thread is displaced stepping is a recipe for
   crashing it, as nothing would readjust the PC out of the scratch
   pad.  */

void
prepare_for_detach (void)
{
  struct inferior *inf = current_inferior ();
  ptid_t pid_ptid = pid_to_ptid (inf->pid);
  struct cleanup *old_chain_1;
  struct displaced_step_inferior_state *displaced;

  displaced = get_displaced_stepping_state (inf->pid);

  /* Is any thread of this process displaced stepping?  If not,
     there's nothing else to do.  */
  if (displaced == NULL || ptid_equal (displaced->step_ptid, null_ptid))
    return;

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
			"displaced-stepping in-process while detaching");

  old_chain_1 = make_cleanup_restore_integer (&inf->detaching);
  inf->detaching = 1;

  while (!ptid_equal (displaced->step_ptid, null_ptid))
    {
      struct cleanup *old_chain_2;
      struct execution_control_state ecss;
      struct execution_control_state *ecs;

      ecs = &ecss;
      memset (ecs, 0, sizeof (*ecs));

      overlay_cache_invalid = 1;

      if (deprecated_target_wait_hook)
	ecs->ptid = deprecated_target_wait_hook (pid_ptid, &ecs->ws, 0);
      else
	ecs->ptid = target_wait (pid_ptid, &ecs->ws, 0);

      if (debug_infrun)
	print_target_wait_results (pid_ptid, ecs->ptid, &ecs->ws);

      /* If an error happens while handling the event, propagate GDB's
	 knowledge of the executing state to the frontend/user running
	 state.  */
      old_chain_2 = make_cleanup (finish_thread_state_cleanup,
				  &minus_one_ptid);

      /* Now figure out what to do with the result of the result.  */
      handle_inferior_event (ecs);

      /* No error, don't finish the state yet.  */
      discard_cleanups (old_chain_2);

      /* Breakpoints and watchpoints are not installed on the target
	 at this point, and signals are passed directly to the
	 inferior, so this must mean the process is gone.  */
      if (!ecs->wait_some_more)
	{
	  discard_cleanups (old_chain_1);
	  error (_("Program exited while detaching"));
	}
    }

  discard_cleanups (old_chain_1);
}

/* Wait for control to return from inferior to debugger.

   If inferior gets a signal, we may decide to start it up again
   instead of returning.  That is why there is a loop in this function.
   When this function actually returns it means the inferior
   should be left stopped and GDB should read more commands.  */

void
wait_for_inferior (void)
{
  struct cleanup *old_cleanups;

  if (debug_infrun)
    fprintf_unfiltered
      (gdb_stdlog, "infrun: wait_for_inferior ()\n");

  old_cleanups =
    make_cleanup (delete_step_thread_step_resume_breakpoint_cleanup, NULL);

  while (1)
    {
      struct execution_control_state ecss;
      struct execution_control_state *ecs = &ecss;
      struct cleanup *old_chain;

      memset (ecs, 0, sizeof (*ecs));

      overlay_cache_invalid = 1;

      if (deprecated_target_wait_hook)
	ecs->ptid = deprecated_target_wait_hook (waiton_ptid, &ecs->ws, 0);
      else
	ecs->ptid = target_wait (waiton_ptid, &ecs->ws, 0);

      if (debug_infrun)
	print_target_wait_results (waiton_ptid, ecs->ptid, &ecs->ws);

      /* If an error happens while handling the event, propagate GDB's
	 knowledge of the executing state to the frontend/user running
	 state.  */
      old_chain = make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);

      /* Now figure out what to do with the result of the result.  */
      handle_inferior_event (ecs);

      /* No error, don't finish the state yet.  */
      discard_cleanups (old_chain);

      if (!ecs->wait_some_more)
	break;
    }

  do_cleanups (old_cleanups);
}

/* Asynchronous version of wait_for_inferior.  It is called by the
   event loop whenever a change of state is detected on the file
   descriptor corresponding to the target.  It can be called more than
   once to complete a single execution command.  In such cases we need
   to keep the state in a global variable ECSS.  If it is the last time
   that this function is called for a single execution command, then
   report to the user that the inferior has stopped, and do the
   necessary cleanups.  */

void
fetch_inferior_event (void *client_data)
{
  struct execution_control_state ecss;
  struct execution_control_state *ecs = &ecss;
  struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
  struct cleanup *ts_old_chain;
  int was_sync = sync_execution;
  int cmd_done = 0;

  memset (ecs, 0, sizeof (*ecs));

  /* We're handling a live event, so make sure we're doing live
     debugging.  If we're looking at traceframes while the target is
     running, we're going to need to get back to that mode after
     handling the event.  */
  if (non_stop)
    {
      make_cleanup_restore_current_traceframe ();
      set_current_traceframe (-1);
    }

  if (non_stop)
    /* In non-stop mode, the user/frontend should not notice a thread
       switch due to internal events.  Make sure we reverse to the
       user selected thread and frame after handling the event and
       running any breakpoint commands.  */
    make_cleanup_restore_current_thread ();

  overlay_cache_invalid = 1;

  make_cleanup_restore_integer (&execution_direction);
  execution_direction = target_execution_direction ();

  if (deprecated_target_wait_hook)
    ecs->ptid =
      deprecated_target_wait_hook (waiton_ptid, &ecs->ws, TARGET_WNOHANG);
  else
    ecs->ptid = target_wait (waiton_ptid, &ecs->ws, TARGET_WNOHANG);

  if (debug_infrun)
    print_target_wait_results (waiton_ptid, ecs->ptid, &ecs->ws);

  /* If an error happens while handling the event, propagate GDB's
     knowledge of the executing state to the frontend/user running
     state.  */
  if (!non_stop)
    ts_old_chain = make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);
  else
    ts_old_chain = make_cleanup (finish_thread_state_cleanup, &ecs->ptid);

  /* Get executed before make_cleanup_restore_current_thread above to apply
     still for the thread which has thrown the exception.  */
  make_bpstat_clear_actions_cleanup ();

  /* Now figure out what to do with the result of the result.  */
  handle_inferior_event (ecs);

  if (!ecs->wait_some_more)
    {
      struct inferior *inf = find_inferior_pid (ptid_get_pid (ecs->ptid));

      delete_step_thread_step_resume_breakpoint ();

      /* We may not find an inferior if this was a process exit.  */
      if (inf == NULL || inf->control.stop_soon == NO_STOP_QUIETLY)
	normal_stop ();

      if (target_has_execution
	  && ecs->ws.kind != TARGET_WAITKIND_NO_RESUMED
	  && ecs->ws.kind != TARGET_WAITKIND_EXITED
	  && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
	  && ecs->event_thread->step_multi
	  && ecs->event_thread->control.stop_step)
	inferior_event_handler (INF_EXEC_CONTINUE, NULL);
      else
	{
	  inferior_event_handler (INF_EXEC_COMPLETE, NULL);
	  cmd_done = 1;
	}
    }

  /* No error, don't finish the thread states yet.  */
  discard_cleanups (ts_old_chain);

  /* Revert thread and frame.  */
  do_cleanups (old_chain);

  /* If the inferior was in sync execution mode, and now isn't,
     restore the prompt (a synchronous execution command has finished,
     and we're ready for input).  */
  if (interpreter_async && was_sync && !sync_execution)
    display_gdb_prompt (0);

  if (cmd_done
      && !was_sync
      && exec_done_display_p
      && (ptid_equal (inferior_ptid, null_ptid)
	  || !is_running (inferior_ptid)))
    printf_unfiltered (_("completed.\n"));
}

/* Record the frame and location we're currently stepping through.  */
void
set_step_info (struct frame_info *frame, struct symtab_and_line sal)
{
  struct thread_info *tp = inferior_thread ();

  tp->control.step_frame_id = get_frame_id (frame);
  tp->control.step_stack_frame_id = get_stack_frame_id (frame);

  tp->current_symtab = sal.symtab;
  tp->current_line = sal.line;
}

/* Clear context switchable stepping state.  */

void
init_thread_stepping_state (struct thread_info *tss)
{
  tss->stepping_over_breakpoint = 0;
  tss->step_after_step_resume_breakpoint = 0;
}

/* Return the cached copy of the last pid/waitstatus returned by
   target_wait()/deprecated_target_wait_hook().  The data is actually
   cached by handle_inferior_event(), which gets called immediately
   after target_wait()/deprecated_target_wait_hook().  */

void
get_last_target_status (ptid_t *ptidp, struct target_waitstatus *status)
{
  *ptidp = target_last_wait_ptid;
  *status = target_last_waitstatus;
}

void
nullify_last_target_wait_ptid (void)
{
  target_last_wait_ptid = minus_one_ptid;
}

/* Switch thread contexts.  */

static void
context_switch (ptid_t ptid)
{
  if (debug_infrun && !ptid_equal (ptid, inferior_ptid))
    {
      fprintf_unfiltered (gdb_stdlog, "infrun: Switching context from %s ",
			  target_pid_to_str (inferior_ptid));
      fprintf_unfiltered (gdb_stdlog, "to %s\n",
			  target_pid_to_str (ptid));
    }

  switch_to_thread (ptid);
}

static void
adjust_pc_after_break (struct execution_control_state *ecs)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  struct address_space *aspace;
  CORE_ADDR breakpoint_pc;

  /* If we've hit a breakpoint, we'll normally be stopped with SIGTRAP.  If
     we aren't, just return.

     We assume that waitkinds other than TARGET_WAITKIND_STOPPED are not
     affected by gdbarch_decr_pc_after_break.  Other waitkinds which are
     implemented by software breakpoints should be handled through the normal
     breakpoint layer.

     NOTE drow/2004-01-31: On some targets, breakpoints may generate
     different signals (SIGILL or SIGEMT for instance), but it is less
     clear where the PC is pointing afterwards.  It may not match
     gdbarch_decr_pc_after_break.  I don't know any specific target that
     generates these signals at breakpoints (the code has been in GDB since at
     least 1992) so I can not guess how to handle them here.

     In earlier versions of GDB, a target with 
     gdbarch_have_nonsteppable_watchpoint would have the PC after hitting a
     watchpoint affected by gdbarch_decr_pc_after_break.  I haven't found any
     target with both of these set in GDB history, and it seems unlikely to be
     correct, so gdbarch_have_nonsteppable_watchpoint is not checked here.  */

  if (ecs->ws.kind != TARGET_WAITKIND_STOPPED)
    return;

  if (ecs->ws.value.sig != GDB_SIGNAL_TRAP)
    return;

  /* In reverse execution, when a breakpoint is hit, the instruction
     under it has already been de-executed.  The reported PC always
     points at the breakpoint address, so adjusting it further would
     be wrong.  E.g., consider this case on a decr_pc_after_break == 1
     architecture:

       B1         0x08000000 :   INSN1
       B2         0x08000001 :   INSN2
		  0x08000002 :   INSN3
	    PC -> 0x08000003 :   INSN4

     Say you're stopped at 0x08000003 as above.  Reverse continuing
     from that point should hit B2 as below.  Reading the PC when the
     SIGTRAP is reported should read 0x08000001 and INSN2 should have
     been de-executed already.

       B1         0x08000000 :   INSN1
       B2   PC -> 0x08000001 :   INSN2
		  0x08000002 :   INSN3
		  0x08000003 :   INSN4

     We can't apply the same logic as for forward execution, because
     we would wrongly adjust the PC to 0x08000000, since there's a
     breakpoint at PC - 1.  We'd then report a hit on B1, although
     INSN1 hadn't been de-executed yet.  Doing nothing is the correct
     behaviour.  */
  if (execution_direction == EXEC_REVERSE)
    return;

  /* If this target does not decrement the PC after breakpoints, then
     we have nothing to do.  */
  regcache = get_thread_regcache (ecs->ptid);
  gdbarch = get_regcache_arch (regcache);
  if (gdbarch_decr_pc_after_break (gdbarch) == 0)
    return;

  aspace = get_regcache_aspace (regcache);

  /* Find the location where (if we've hit a breakpoint) the
     breakpoint would be.  */
  breakpoint_pc = regcache_read_pc (regcache)
		  - gdbarch_decr_pc_after_break (gdbarch);

  /* Check whether there actually is a software breakpoint inserted at
     that location.

     If in non-stop mode, a race condition is possible where we've
     removed a breakpoint, but stop events for that breakpoint were
     already queued and arrive later.  To suppress those spurious
     SIGTRAPs, we keep a list of such breakpoint locations for a bit,
     and retire them after a number of stop events are reported.  */
  if (software_breakpoint_inserted_here_p (aspace, breakpoint_pc)
      || (non_stop && moribund_breakpoint_here_p (aspace, breakpoint_pc)))
    {
      struct cleanup *old_cleanups = NULL;

      if (RECORD_IS_USED)
	old_cleanups = record_gdb_operation_disable_set ();

      /* When using hardware single-step, a SIGTRAP is reported for both
	 a completed single-step and a software breakpoint.  Need to
	 differentiate between the two, as the latter needs adjusting
	 but the former does not.

	 The SIGTRAP can be due to a completed hardware single-step only if 
	  - we didn't insert software single-step breakpoints
	  - the thread to be examined is still the current thread
	  - this thread is currently being stepped

	 If any of these events did not occur, we must have stopped due
	 to hitting a software breakpoint, and have to back up to the
	 breakpoint address.

	 As a special case, we could have hardware single-stepped a
	 software breakpoint.  In this case (prev_pc == breakpoint_pc),
	 we also need to back up to the breakpoint address.  */

      if (singlestep_breakpoints_inserted_p
	  || !ptid_equal (ecs->ptid, inferior_ptid)
	  || !currently_stepping (ecs->event_thread)
	  || ecs->event_thread->prev_pc == breakpoint_pc)
	regcache_write_pc (regcache, breakpoint_pc);

      if (RECORD_IS_USED)
	do_cleanups (old_cleanups);
    }
}

void
init_infwait_state (void)
{
  waiton_ptid = pid_to_ptid (-1);
  infwait_state = infwait_normal_state;
}

void
error_is_running (void)
{
  error (_("Cannot execute this command while "
	   "the selected thread is running."));
}

void
ensure_not_running (void)
{
  if (is_running (inferior_ptid))
    error_is_running ();
}

static int
stepped_in_from (struct frame_info *frame, struct frame_id step_frame_id)
{
  for (frame = get_prev_frame (frame);
       frame != NULL;
       frame = get_prev_frame (frame))
    {
      if (frame_id_eq (get_frame_id (frame), step_frame_id))
	return 1;
      if (get_frame_type (frame) != INLINE_FRAME)
	break;
    }

  return 0;
}

/* Auxiliary function that handles syscall entry/return events.
   It returns 1 if the inferior should keep going (and GDB
   should ignore the event), or 0 if the event deserves to be
   processed.  */

static int
handle_syscall_event (struct execution_control_state *ecs)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  int syscall_number;

  if (!ptid_equal (ecs->ptid, inferior_ptid))
    context_switch (ecs->ptid);

  regcache = get_thread_regcache (ecs->ptid);
  gdbarch = get_regcache_arch (regcache);
  syscall_number = ecs->ws.value.syscall_number;
  stop_pc = regcache_read_pc (regcache);

  if (catch_syscall_enabled () > 0
      && catching_syscall_number (syscall_number) > 0)
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: syscall number = '%d'\n",
                            syscall_number);

      ecs->event_thread->control.stop_bpstat
	= bpstat_stop_status (get_regcache_aspace (regcache),
			      stop_pc, ecs->ptid, &ecs->ws);
      ecs->random_signal
	= !bpstat_explains_signal (ecs->event_thread->control.stop_bpstat);

      if (!ecs->random_signal)
	{
	  /* Catchpoint hit.  */
	  ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_TRAP;
	  return 0;
	}
    }

  /* If no catchpoint triggered for this, then keep going.  */
  ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
  keep_going (ecs);
  return 1;
}

/* Clear the supplied execution_control_state's stop_func_* fields.  */

static void
clear_stop_func (struct execution_control_state *ecs)
{
  ecs->stop_func_filled_in = 0;
  ecs->stop_func_start = 0;
  ecs->stop_func_end = 0;
  ecs->stop_func_name = NULL;
}

/* Lazily fill in the execution_control_state's stop_func_* fields.  */

static void
fill_in_stop_func (struct gdbarch *gdbarch,
		   struct execution_control_state *ecs)
{
  if (!ecs->stop_func_filled_in)
    {
      /* Don't care about return value; stop_func_start and stop_func_name
	 will both be 0 if it doesn't work.  */
      find_pc_partial_function (stop_pc, &ecs->stop_func_name,
				&ecs->stop_func_start, &ecs->stop_func_end);
      ecs->stop_func_start
	+= gdbarch_deprecated_function_start_offset (gdbarch);

      ecs->stop_func_filled_in = 1;
    }
}

/* Given an execution control state that has been freshly filled in
   by an event from the inferior, figure out what it means and take
   appropriate action.  */

static void
handle_inferior_event (struct execution_control_state *ecs)
{
  struct frame_info *frame;
  struct gdbarch *gdbarch;
  int stopped_by_watchpoint;
  int stepped_after_stopped_by_watchpoint = 0;
  struct symtab_and_line stop_pc_sal;
  enum stop_kind stop_soon;

  if (ecs->ws.kind == TARGET_WAITKIND_IGNORE)
    {
      /* We had an event in the inferior, but we are not interested in
	 handling it at this level.  The lower layers have already
	 done what needs to be done, if anything.

	 One of the possible circumstances for this is when the
	 inferior produces output for the console.  The inferior has
	 not stopped, and we are ignoring the event.  Another possible
	 circumstance is any event which the lower level knows will be
	 reported multiple times without an intervening resume.  */
      if (debug_infrun)
	fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_IGNORE\n");
      prepare_to_wait (ecs);
      return;
    }

  if (ecs->ws.kind == TARGET_WAITKIND_NO_RESUMED
      && target_can_async_p () && !sync_execution)
    {
      /* There were no unwaited-for children left in the target, but,
	 we're not synchronously waiting for events either.  Just
	 ignore.  Otherwise, if we were running a synchronous
	 execution command, we need to cancel it and give the user
	 back the terminal.  */
      if (debug_infrun)
	fprintf_unfiltered (gdb_stdlog,
			    "infrun: TARGET_WAITKIND_NO_RESUMED (ignoring)\n");
      prepare_to_wait (ecs);
      return;
    }

  if (ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
      && ecs->ws.kind != TARGET_WAITKIND_NO_RESUMED)
    {
      struct inferior *inf = find_inferior_pid (ptid_get_pid (ecs->ptid));

      gdb_assert (inf);
      stop_soon = inf->control.stop_soon;
    }
  else
    stop_soon = NO_STOP_QUIETLY;

  /* Cache the last pid/waitstatus.  */
  target_last_wait_ptid = ecs->ptid;
  target_last_waitstatus = ecs->ws;

  /* Always clear state belonging to the previous time we stopped.  */
  stop_stack_dummy = STOP_NONE;

  if (ecs->ws.kind == TARGET_WAITKIND_NO_RESUMED)
    {
      /* No unwaited-for children left.  IOW, all resumed children
	 have exited.  */
      if (debug_infrun)
	fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_NO_RESUMED\n");

      stop_print_frame = 0;
      stop_stepping (ecs);
      return;
    }

  if (ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
      && !ptid_equal (ecs->ptid, minus_one_ptid))
    {
      ecs->event_thread = find_thread_ptid (ecs->ptid);
      /* If it's a new thread, add it to the thread database.  */
      if (ecs->event_thread == NULL)
	ecs->event_thread = add_thread (ecs->ptid);
    }

  /* Dependent on valid ECS->EVENT_THREAD.  */
  adjust_pc_after_break (ecs);

  /* Dependent on the current PC value modified by adjust_pc_after_break.  */
  reinit_frame_cache ();

  breakpoint_retire_moribund ();

  /* First, distinguish signals caused by the debugger from signals
     that have to do with the program's own actions.  Note that
     breakpoint insns may cause SIGTRAP or SIGILL or SIGEMT, depending
     on the operating system version.  Here we detect when a SIGILL or
     SIGEMT is really a breakpoint and change it to SIGTRAP.  We do
     something similar for SIGSEGV, since a SIGSEGV will be generated
     when we're trying to execute a breakpoint instruction on a
     non-executable stack.  This happens for call dummy breakpoints
     for architectures like SPARC that place call dummies on the
     stack.  */
  if (ecs->ws.kind == TARGET_WAITKIND_STOPPED
      && (ecs->ws.value.sig == GDB_SIGNAL_ILL
	  || ecs->ws.value.sig == GDB_SIGNAL_SEGV
	  || ecs->ws.value.sig == GDB_SIGNAL_EMT))
    {
      struct regcache *regcache = get_thread_regcache (ecs->ptid);

      if (breakpoint_inserted_here_p (get_regcache_aspace (regcache),
				      regcache_read_pc (regcache)))
	{
	  if (debug_infrun)
	    fprintf_unfiltered (gdb_stdlog,
				"infrun: Treating signal as SIGTRAP\n");
	  ecs->ws.value.sig = GDB_SIGNAL_TRAP;
	}
    }

  /* Mark the non-executing threads accordingly.  In all-stop, all
     threads of all processes are stopped when we get any event
     reported.  In non-stop mode, only the event thread stops.  If
     we're handling a process exit in non-stop mode, there's nothing
     to do, as threads of the dead process are gone, and threads of
     any other process were left running.  */
  if (!non_stop)
    set_executing (minus_one_ptid, 0);
  else if (ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
	   && ecs->ws.kind != TARGET_WAITKIND_EXITED)
    set_executing (ecs->ptid, 0);

  switch (infwait_state)
    {
    case infwait_thread_hop_state:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: infwait_thread_hop_state\n");
      break;

    case infwait_normal_state:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: infwait_normal_state\n");
      break;

    case infwait_step_watch_state:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
			    "infrun: infwait_step_watch_state\n");

      stepped_after_stopped_by_watchpoint = 1;
      break;

    case infwait_nonstep_watch_state:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
			    "infrun: infwait_nonstep_watch_state\n");
      insert_breakpoints ();

      /* FIXME-maybe: is this cleaner than setting a flag?  Does it
         handle things like signals arriving and other things happening
         in combination correctly?  */
      stepped_after_stopped_by_watchpoint = 1;
      break;

    default:
      internal_error (__FILE__, __LINE__, _("bad switch"));
    }

  infwait_state = infwait_normal_state;
  waiton_ptid = pid_to_ptid (-1);

  switch (ecs->ws.kind)
    {
    case TARGET_WAITKIND_LOADED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_LOADED\n");
      /* Ignore gracefully during startup of the inferior, as it might
         be the shell which has just loaded some objects, otherwise
         add the symbols for the newly loaded objects.  Also ignore at
         the beginning of an attach or remote session; we will query
         the full list of libraries once the connection is
         established.  */
      if (stop_soon == NO_STOP_QUIETLY)
	{
	  struct regcache *regcache;

	  if (!ptid_equal (ecs->ptid, inferior_ptid))
	    context_switch (ecs->ptid);
	  regcache = get_thread_regcache (ecs->ptid);

	  handle_solib_event ();

	  ecs->event_thread->control.stop_bpstat
	    = bpstat_stop_status (get_regcache_aspace (regcache),
				  stop_pc, ecs->ptid, &ecs->ws);
	  ecs->random_signal
	    = !bpstat_explains_signal (ecs->event_thread->control.stop_bpstat);

	  if (!ecs->random_signal)
	    {
	      /* A catchpoint triggered.  */
	      ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_TRAP;
	      goto process_event_stop_test;
	    }

	  /* If requested, stop when the dynamic linker notifies
	     gdb of events.  This allows the user to get control
	     and place breakpoints in initializer routines for
	     dynamically loaded objects (among other things).  */
	  ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
	  if (stop_on_solib_events)
	    {
	      /* Make sure we print "Stopped due to solib-event" in
		 normal_stop.  */
	      stop_print_frame = 1;

	      stop_stepping (ecs);
	      return;
	    }
	}

      /* If we are skipping through a shell, or through shared library
	 loading that we aren't interested in, resume the program.  If
	 we're running the program normally, also resume.  But stop if
	 we're attaching or setting up a remote connection.  */
      if (stop_soon == STOP_QUIETLY || stop_soon == NO_STOP_QUIETLY)
	{
	  if (!ptid_equal (ecs->ptid, inferior_ptid))
	    context_switch (ecs->ptid);

	  /* Loading of shared libraries might have changed breakpoint
	     addresses.  Make sure new breakpoints are inserted.  */
	  if (stop_soon == NO_STOP_QUIETLY
	      && !breakpoints_always_inserted_mode ())
	    insert_breakpoints ();
	  resume (0, GDB_SIGNAL_0);
	  prepare_to_wait (ecs);
	  return;
	}

      break;

    case TARGET_WAITKIND_SPURIOUS:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_SPURIOUS\n");
      if (!ptid_equal (ecs->ptid, inferior_ptid)
	  && !ptid_equal (ecs->ptid, minus_one_ptid))
	context_switch (ecs->ptid);
      resume (0, GDB_SIGNAL_0);
      prepare_to_wait (ecs);
      return;

    case TARGET_WAITKIND_EXITED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_EXITED\n");
      inferior_ptid = ecs->ptid;
      set_current_inferior (find_inferior_pid (ptid_get_pid (ecs->ptid)));
      set_current_program_space (current_inferior ()->pspace);
      handle_vfork_child_exec_or_exit (0);
      target_terminal_ours ();	/* Must do this before mourn anyway.  */
      print_exited_reason (ecs->ws.value.integer);

      /* Record the exit code in the convenience variable $_exitcode, so
         that the user can inspect this again later.  */
      set_internalvar_integer (lookup_internalvar ("_exitcode"),
			       (LONGEST) ecs->ws.value.integer);

      /* Also record this in the inferior itself.  */
      current_inferior ()->has_exit_code = 1;
      current_inferior ()->exit_code = (LONGEST) ecs->ws.value.integer;

      gdb_flush (gdb_stdout);
      target_mourn_inferior ();
      singlestep_breakpoints_inserted_p = 0;
      cancel_single_step_breakpoints ();
      stop_print_frame = 0;
      stop_stepping (ecs);
      return;

    case TARGET_WAITKIND_SIGNALLED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_SIGNALLED\n");
      inferior_ptid = ecs->ptid;
      set_current_inferior (find_inferior_pid (ptid_get_pid (ecs->ptid)));
      set_current_program_space (current_inferior ()->pspace);
      handle_vfork_child_exec_or_exit (0);
      stop_print_frame = 0;
      target_terminal_ours ();	/* Must do this before mourn anyway.  */

      /* Note: By definition of TARGET_WAITKIND_SIGNALLED, we shouldn't
         reach here unless the inferior is dead.  However, for years
         target_kill() was called here, which hints that fatal signals aren't
         really fatal on some systems.  If that's true, then some changes
         may be needed.  */
      target_mourn_inferior ();

      print_signal_exited_reason (ecs->ws.value.sig);
      singlestep_breakpoints_inserted_p = 0;
      cancel_single_step_breakpoints ();
      stop_stepping (ecs);
      return;

      /* The following are the only cases in which we keep going;
         the above cases end in a continue or goto.  */
    case TARGET_WAITKIND_FORKED:
    case TARGET_WAITKIND_VFORKED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_FORKED\n");

      /* Check whether the inferior is displaced stepping.  */
      {
	struct regcache *regcache = get_thread_regcache (ecs->ptid);
	struct gdbarch *gdbarch = get_regcache_arch (regcache);
	struct displaced_step_inferior_state *displaced
	  = get_displaced_stepping_state (ptid_get_pid (ecs->ptid));

	/* If checking displaced stepping is supported, and thread
	   ecs->ptid is displaced stepping.  */
	if (displaced && ptid_equal (displaced->step_ptid, ecs->ptid))
	  {
	    struct inferior *parent_inf
	      = find_inferior_pid (ptid_get_pid (ecs->ptid));
	    struct regcache *child_regcache;
	    CORE_ADDR parent_pc;

	    /* GDB has got TARGET_WAITKIND_FORKED or TARGET_WAITKIND_VFORKED,
	       indicating that the displaced stepping of syscall instruction
	       has been done.  Perform cleanup for parent process here.  Note
	       that this operation also cleans up the child process for vfork,
	       because their pages are shared.  */