/* Ada Ravenscar thread support.

   Copyright 2004, 2009-2012 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 "gdbcore.h"
#include "gdbthread.h"
#include "ada-lang.h"
#include "target.h"
#include "inferior.h"
#include "command.h"
#include "ravenscar-thread.h"
#include "observer.h"
#include "gdb_string.h"
#include "gdbcmd.h"
#include "top.h"
#include "regcache.h"

/* If non-null, ravenscar task support is enabled.  */
static int ravenscar_task_support = 1;

/* Non-null if the ravenscar thread layer has been pushed on the target
   stack.  */
static int ravenscar_is_open = 0;

/* This module's target-specific operations.  */
static struct target_ops ravenscar_ops;

/* Some base target uses a special value for the null PID (exempli gratia
   remote).  */
static ptid_t base_magic_null_ptid;

/* Ptid of the inferior as seen by the process stratum.  */
static ptid_t base_ptid;

static const char running_thread_name[] = "__gnat_running_thread_table";

static const char known_tasks_name[] = "system__tasking__debug__known_tasks";
static const char first_task_name[] = "system__tasking__debug__first_task";

static const char ravenscar_runtime_initializer[] =
  "system__bb__threads__initialize";

static struct observer *update_target_observer = NULL;

/* Architecture-specific hooks.  */
static struct ravenscar_arch_ops* current_arch_ops;

static void ravenscar_find_new_threads (struct target_ops *ops);
static ptid_t ravenscar_running_thread (void);
static char *ravenscar_extra_thread_info (struct thread_info *tp);
static int ravenscar_thread_alive (struct target_ops *ops, ptid_t ptid);
static void ravenscar_fetch_registers (struct target_ops *ops,
                                       struct regcache *regcache, int regnum);
static void ravenscar_store_registers (struct target_ops *ops,
                                       struct regcache *regcache, int regnum);
static void ravenscar_prepare_to_store (struct regcache *regcache);
static void ravenscar_initialize  (char *name, int from_tty);
static void ravenscar_resume (struct target_ops *ops, ptid_t ptid, int step,
			      enum target_signal siggnal);
static void ravenscar_mourn_inferior (struct target_ops *ops);
static void ravenscar_update_inferior_ptid (void);
static int has_ravenscar_runtime (void);
static int ravenscar_runtime_initialized (void);
static void ravenscar_inferior_created (struct target_ops *target,
					int from_tty);

/* Fetch the ravenscar running thread from target memory and
   update inferior_ptid accordingly.  */

static void
ravenscar_update_inferior_ptid (void)
{
  base_ptid = inferior_ptid;

  /* If the runtime has not been initialized yet, the inferior_ptid is
     the only ptid that there is.  */
  if (!ravenscar_runtime_initialized ())
    return;

  /* Make sure we set base_ptid before calling ravenscar_running_thread
     as the latter relies on it.  */
  inferior_ptid = ravenscar_running_thread ();
  gdb_assert (!ptid_equal (inferior_ptid, null_ptid));

  /* The running thread may not have been added to
     system.tasking.debug's list yet; so ravenscar_find_new_threads
     may not always add it to the thread list.  Add it here.  */
  if (!find_thread_ptid (inferior_ptid))
    add_thread (inferior_ptid);
}

/* The Ravenscar Runtime exports a symbol which contains the ID of
   the thread that is currently running.  Try to locate that symbol
   and return its associated minimal symbol.
   Return NULL if not found.  */

static struct minimal_symbol *
get_running_thread_msymbol (void)
{
  struct minimal_symbol *msym;

  msym = lookup_minimal_symbol (running_thread_name, NULL, NULL);
  if (!msym)
    /* Older versions of the GNAT runtime were using a different
       (less ideal) name for the symbol where the active thread ID
       is stored.  If we couldn't find the symbol using the latest
       name, then try the old one.  */
    msym = lookup_minimal_symbol ("running_thread", NULL, NULL);

  return msym;
}

/* Return True if the Ada Ravenscar run-time can be found in the
   application.  */

static int
has_ravenscar_runtime (void)
{
  struct minimal_symbol *msym_ravenscar_runtime_initializer =
    lookup_minimal_symbol (ravenscar_runtime_initializer, NULL, NULL);
  struct minimal_symbol *msym_known_tasks =
    lookup_minimal_symbol (known_tasks_name, NULL, NULL);
  struct minimal_symbol *msym_first_task =
    lookup_minimal_symbol (first_task_name, NULL, NULL);
  struct minimal_symbol *msym_running_thread = get_running_thread_msymbol ();

  return (msym_ravenscar_runtime_initializer
	  && (msym_known_tasks || msym_first_task)
	  && msym_running_thread);
}

/* Return True if the Ada Ravenscar run-time can be found in the
   application, and if it has been initialized on target.  */

static int
ravenscar_runtime_initialized (void)
{
  return (!(ptid_equal (ravenscar_running_thread (), null_ptid)));
}

/* Return the ID of the thread that is currently running.
   Return 0 if the ID could not be determined.  */

static CORE_ADDR
get_running_thread_id (void)
{
  const struct minimal_symbol *object_msym = get_running_thread_msymbol ();
  int object_size;
  int buf_size;
  char *buf;
  CORE_ADDR object_addr;
  struct type *builtin_type_void_data_ptr =
    builtin_type (target_gdbarch)->builtin_data_ptr;

  if (!object_msym)
    return 0;

  object_addr = SYMBOL_VALUE_ADDRESS (object_msym);
  object_size = TYPE_LENGTH (builtin_type_void_data_ptr);
  buf_size = object_size;
  buf = alloca (buf_size);
  read_memory (object_addr, buf, buf_size);
  return extract_typed_address (buf, builtin_type_void_data_ptr);
}

static void
ravenscar_close (int quitting)
{
  ravenscar_is_open = 0;
}

static void
ravenscar_resume (struct target_ops *ops, ptid_t ptid, int step,
		  enum target_signal siggnal)
{
  struct target_ops *beneath = find_target_beneath (ops);

  inferior_ptid = base_ptid;
  beneath->to_resume (beneath, base_ptid, step, siggnal);
}

static ptid_t
ravenscar_wait (struct target_ops *ops, ptid_t ptid,
                struct target_waitstatus *status,
                int options)
{
  struct target_ops *beneath = find_target_beneath (ops);

  inferior_ptid = base_ptid;
  beneath->to_wait (beneath, base_ptid, status, 0);
  ravenscar_find_new_threads (ops);
  ravenscar_update_inferior_ptid ();
  return inferior_ptid;
}

/* Add the thread associated to the given TASK to the thread list
   (if the thread has already been added, this is a no-op).  */

static void
ravenscar_add_thread (struct ada_task_info *task)
{
  if (find_thread_ptid (task->ptid) == NULL)
    add_thread (task->ptid);
}

static void
ravenscar_find_new_threads (struct target_ops *ops)
{
  ada_build_task_list ();

  /* Do not clear the thread list before adding the Ada task, to keep
     the thread that the process stratum has included into it
     (base_ptid) and the running thread, that may not have been included
     to system.tasking.debug's list yet.  */

  iterate_over_live_ada_tasks (ravenscar_add_thread);
}

static ptid_t
ravenscar_running_thread (void)
{
  CORE_ADDR tid = get_running_thread_id ();

  if (tid == 0)
    return null_ptid;
  else
    return ptid_build (ptid_get_pid (base_ptid), 0, tid);
}

static char *
ravenscar_extra_thread_info (struct thread_info *tp)
{
  return "Ravenscar task";
}

static int
ravenscar_thread_alive (struct target_ops *ops, ptid_t ptid)
{
  /* Ravenscar tasks are non-terminating.  */
  return 1;
}

static char *
ravenscar_pid_to_str (struct target_ops *ops, ptid_t ptid)
{
  static char buf[30];

  snprintf (buf, sizeof (buf), "Thread %#x", (int) ptid_get_tid (ptid));
  return buf;
}

static void
ravenscar_fetch_registers (struct target_ops *ops,
                           struct regcache *regcache, int regnum)
{
  struct target_ops *beneath = find_target_beneath (ops);

  if (!ravenscar_runtime_initialized ()
      || ptid_equal (inferior_ptid, base_magic_null_ptid)
      || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
    beneath->to_fetch_registers (beneath, regcache, regnum);
  else
    current_arch_ops->to_fetch_registers (regcache, regnum);
}

static void
ravenscar_store_registers (struct target_ops *ops,
                           struct regcache *regcache, int regnum)
{
  struct target_ops *beneath = find_target_beneath (ops);

  if (!ravenscar_runtime_initialized ()
      || ptid_equal (inferior_ptid, base_magic_null_ptid)
      || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
    beneath->to_store_registers (beneath, regcache, regnum);
  else
    current_arch_ops->to_store_registers (regcache, regnum);
}

static void
ravenscar_prepare_to_store (struct regcache *regcache)
{
  struct target_ops *beneath = find_target_beneath (&ravenscar_ops);

  if (!ravenscar_runtime_initialized ()
      || ptid_equal (inferior_ptid, base_magic_null_ptid)
      || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
    beneath->to_prepare_to_store (regcache);
  else
    current_arch_ops->to_prepare_to_store (regcache);
}

static void
ravenscar_mourn_inferior (struct target_ops *ops)
{
  struct target_ops *beneath = find_target_beneath (&ravenscar_ops);

  base_ptid = null_ptid;
  beneath->to_mourn_inferior (beneath);
  unpush_target (&ravenscar_ops);
}

/* Observer on inferior_created: push ravenscar thread stratum if needed.  */

static void
ravenscar_inferior_created (struct target_ops *target, int from_tty)
{
  if (ravenscar_task_support
      && has_ravenscar_runtime ())
    ravenscar_initialize (NULL, 0);
}

void
ravenscar_register_arch_ops (struct ravenscar_arch_ops *ops)
{
  /* FIXME: To be clean, we would need to handle a list of
     architectures, just like in remote-wtx-hw.c.  However, for now the
     only Ravenscar run-time for bare board that is implemented in
     GNAT is for only one architecture: erc32-elf.  So no need to care about
     that for now...  */
  current_arch_ops = ops;
}

/* Initialize Ravenscar support.  */

static void
ravenscar_initialize (char *name, int from_tty)
{
  if (ravenscar_is_open)
    return;

  base_magic_null_ptid = inferior_ptid;
  ravenscar_update_inferior_ptid ();
  push_target (&ravenscar_ops);
  ravenscar_is_open = 1;
}

static ptid_t
ravenscar_get_ada_task_ptid (long lwp, long thread)
{
  return ptid_build (ptid_get_pid (base_ptid), 0, thread);
}

static void
init_ravenscar_thread_ops (void)
{
  ravenscar_ops.to_shortname = "ravenscar";
  ravenscar_ops.to_longname = "Ravenscar tasks.";
  ravenscar_ops.to_doc = "Ravenscar tasks support.";
  ravenscar_ops.to_close = ravenscar_close;
  ravenscar_ops.to_resume = ravenscar_resume;
  ravenscar_ops.to_wait = ravenscar_wait;
  ravenscar_ops.to_fetch_registers = ravenscar_fetch_registers;
  ravenscar_ops.to_store_registers = ravenscar_store_registers;
  ravenscar_ops.to_prepare_to_store = ravenscar_prepare_to_store;
  ravenscar_ops.to_thread_alive = ravenscar_thread_alive;
  ravenscar_ops.to_find_new_threads = ravenscar_find_new_threads;
  ravenscar_ops.to_pid_to_str = ravenscar_pid_to_str;
  ravenscar_ops.to_extra_thread_info = ravenscar_extra_thread_info;
  ravenscar_ops.to_get_ada_task_ptid = ravenscar_get_ada_task_ptid;
  ravenscar_ops.to_mourn_inferior = ravenscar_mourn_inferior;
  ravenscar_ops.to_has_all_memory = default_child_has_all_memory;
  ravenscar_ops.to_has_memory = default_child_has_memory;
  ravenscar_ops.to_has_stack = default_child_has_stack;
  ravenscar_ops.to_has_registers = default_child_has_registers;
  ravenscar_ops.to_has_execution = default_child_has_execution;
  ravenscar_ops.to_stratum = thread_stratum;
  ravenscar_ops.to_magic = OPS_MAGIC;
}

/* Command-list for the "set/show ravenscar" prefix command.  */
static struct cmd_list_element *set_ravenscar_list;
static struct cmd_list_element *show_ravenscar_list;

/* Implement the "set ravenscar" prefix command.  */

static void
set_ravenscar_command (char *arg, int from_tty)
{
  printf_unfiltered (_(\
"\"set ravenscar\" must be followed by the name of a setting.\n"));
  help_list (set_ravenscar_list, "set ravenscar ", -1, gdb_stdout);
}

/* Implement the "show ravenscar" prefix command.  */

static void
show_ravenscar_command (char *args, int from_tty)
{
  cmd_show_list (show_ravenscar_list, from_tty, "");
}

/* Implement the "show ravenscar task-switching" command.  */

static void
show_ravenscar_task_switching_command (struct ui_file *file, int from_tty,
				       struct cmd_list_element *c,
				       const char *value)
{
  if (ravenscar_task_support)
    fprintf_filtered (file, _("\
Support for Ravenscar task/thread switching is enabled\n"));
  else
    fprintf_filtered (file, _("\
Support for Ravenscar task/thread switching is disabled\n"));
}

/* Module startup initialization function, automagically called by
   init.c.  */

void
_initialize_ravenscar (void)
{
  init_ravenscar_thread_ops ();
  base_ptid = null_ptid;

  /* Notice when the inferior is created in order to push the
     ravenscar ops if needed.  */
  observer_attach_inferior_created (ravenscar_inferior_created);

  add_target (&ravenscar_ops);

  add_prefix_cmd ("ravenscar", no_class, set_ravenscar_command,
                  _("Prefix command for changing Ravenscar-specific settings"),
                  &set_ravenscar_list, "set ravenscar ", 0, &setlist);

  add_prefix_cmd ("ravenscar", no_class, show_ravenscar_command,
                  _("Prefix command for showing Ravenscar-specific settings"),
                  &show_ravenscar_list, "show ravenscar ", 0, &showlist);

  add_setshow_boolean_cmd ("task-switching", class_obscure,
                           &ravenscar_task_support, _("\
Enable or disable support for GNAT Ravenscar tasks"), _("\
Show whether support for GNAT Ravenscar tasks is enabled"),
                           _("\
Enable or disable support for task/thread switching with the GNAT\n\
Ravenscar run-time library for bareboard configuration."),
			   NULL, show_ravenscar_task_switching_command,
			   &set_ravenscar_list, &show_ravenscar_list);
}