Add support for GNAT Ravenscar run-time library.

gdb/ChangeLog (Jerome Guitton, Joel Brobecker):

	* ravenscar-thread.c, ravenscar-thread.h, ravenscar-sparc-thread.c:
	New files.
	* configure.tgt (sparc-*-*): Add ravenscar-thread.o and
	ravenscar-sparc-thread.o to gdb_target_obs.

5 files changed, 670 insertions, 1 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 416f5a9..0044064 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,4 +1,12 @@
 2010-09-28  Joel Brobecker  <brobecker@adacore.com>
+	    Jerome Guitton  <guitton@adacore.com>
+
+	* ravenscar-thread.c, ravenscar-thread.h, ravenscar-sparc-thread.c:
+	New files.
+	* configure.tgt (sparc-*-*): Add ravenscar-thread.o and
+	ravenscar-sparc-thread.o to gdb_target_obs.
+
+2010-09-28  Joel Brobecker  <brobecker@adacore.com>
 
 	* ada-tasks.c (iterate_over_live_ada_tasks): New function.
 	* ada-lang.h (iterate_over_live_ada_tasks): Declare.
diff --git a/gdb/configure.tgt b/gdb/configure.tgt
index 0b44005..80cfb49 100644
--- a/gdb/configure.tgt
+++ b/gdb/configure.tgt
@@ -521,7 +521,8 @@ sparc-*-rtems*)
 	;;
 sparc-*-*)
 	# Target: SPARC
-	gdb_target_obs="sparc-tdep.o"
+	gdb_target_obs="sparc-tdep.o ravenscar-thread.o \
+			ravenscar-sparc-thread.o"
 	;;
 sparc64-*-*)
 	# Target: UltraSPARC
diff --git a/gdb/ravenscar-sparc-thread.c b/gdb/ravenscar-sparc-thread.c
new file mode 100644
index 0000000..197b745
--- /dev/null
+++ b/gdb/ravenscar-sparc-thread.c
@@ -0,0 +1,185 @@
+/* Ravenscar SPARC target support.
+
+   Copyright 2004, 2010 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 "regcache.h"
+#include "sparc-tdep.h"
+#include "inferior.h"
+#include "ravenscar-thread.h"
+
+static struct ravenscar_arch_ops ravenscar_sparc_ops;
+
+static void ravenscar_sparc_fetch_registers (struct regcache *regcache,
+                                             int regnum);
+static void ravenscar_sparc_store_registers (struct regcache *regcache,
+                                             int regnum);
+static void ravenscar_sparc_prepare_to_store (struct regcache *regcache);
+
+/* Register offsets from a referenced address (exempli gratia the
+   Thread_Descriptor). The referenced address depends on the register
+   number. The Thread_Descriptor layout and the stack layout are documented
+   in the GNAT sources, in sparc-bb.h.  */
+
+static const int sparc_register_offsets[] =
+{
+  /* G0 - G7 */
+  -1,   0x24, 0x28, 0x2C, 0x30, 0x34, 0x38, 0x3C,
+  /* O0 - O7 */
+  0x00, 0x04, 0x08, 0x0C, 0x10, 0x14, 0x18, 0x1C,
+  /* L0 - L7 */
+  0x00, 0x04, 0x08, 0x0C, 0x10, 0x14, 0x18, 0x1C,
+  /* I0 - I7 */
+  0x20, 0x24, 0x28, 0x2C, 0x30, 0x34, 0x38, 0x3C,
+  /* F0 - F31 */
+  0x50, 0x54, 0x58, 0x5C, 0x60, 0x64, 0x68, 0x6C,
+  0x70, 0x74, 0x78, 0x7C, 0x80, 0x84, 0x88, 0x8C,
+  0x90, 0x94, 0x99, 0x9C, 0xA0, 0xA4, 0xA8, 0xAC,
+  0xB0, 0xB4, 0xBB, 0xBC, 0xC0, 0xC4, 0xC8, 0xCC,
+  /* Y  PSR   WIM   TBR   PC    NPC   FPSR  CPSR */
+  0x40, 0x20, 0x44, -1,   0x1C, -1,   0x4C, -1
+};
+
+/* supply register REGNUM, which has been saved on REGISTER_ADDR, to the
+   regcache.  */
+
+static void
+supply_register_at_address (struct regcache *regcache, int regnum,
+                            CORE_ADDR register_addr)
+{
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
+  int buf_size = register_size (gdbarch, regnum);
+  char *buf;
+
+  buf = (char *) alloca (buf_size);
+  read_memory (register_addr, buf, buf_size);
+  regcache_raw_supply (regcache, regnum, &buf);
+}
+
+/* Return true if, for a non-running thread, REGNUM has been saved on the
+   stack.  */
+
+static int
+register_on_stack_p (int regnum)
+{
+  return (regnum >= SPARC_L0_REGNUM && regnum <= SPARC_L7_REGNUM)
+    || (regnum >= SPARC_I0_REGNUM && regnum <= SPARC_I7_REGNUM);
+}
+
+/* Return true if, for a non-running thread, REGNUM has been saved on the
+   Thread_Descriptor.  */
+
+static int
+register_in_thread_descriptor_p (int regnum)
+{
+  return (regnum >= SPARC_O0_REGNUM && regnum <= SPARC_O7_REGNUM)
+    || (regnum == SPARC32_PSR_REGNUM)
+    || (regnum >= SPARC_G1_REGNUM && regnum <= SPARC_G7_REGNUM)
+    || (regnum == SPARC32_Y_REGNUM)
+    || (regnum == SPARC32_WIM_REGNUM)
+    || (regnum == SPARC32_FSR_REGNUM)
+    || (regnum >= SPARC_F0_REGNUM && regnum <= SPARC_F0_REGNUM + 31)
+    || (regnum == SPARC32_PC_REGNUM);
+}
+
+/* to_fetch_registers when inferior_ptid is different from the running
+   thread.  */
+
+static void
+ravenscar_sparc_fetch_registers (struct regcache *regcache, int regnum)
+{
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
+  const int sp_regnum = gdbarch_sp_regnum (gdbarch);
+  const int num_regs = gdbarch_num_regs (gdbarch);
+  int current_regnum;
+  CORE_ADDR current_address;
+  CORE_ADDR thread_descriptor_address;
+  ULONGEST stack_address;
+
+  thread_descriptor_address = (CORE_ADDR) ptid_get_tid (inferior_ptid);
+  current_address = thread_descriptor_address
+    + sparc_register_offsets [sp_regnum];
+  supply_register_at_address (regcache, sp_regnum, current_address);
+  regcache_cooked_read_unsigned (regcache, sp_regnum, &stack_address);
+
+  for (current_regnum = 0; current_regnum < num_regs; current_regnum ++)
+    {
+      if (register_in_thread_descriptor_p (current_regnum))
+        {
+          current_address = thread_descriptor_address
+            + sparc_register_offsets [current_regnum];
+          supply_register_at_address (regcache, current_regnum,
+                                      current_address);
+        }
+      else if (register_on_stack_p (current_regnum))
+        {
+          current_address = stack_address
+            + sparc_register_offsets [current_regnum];
+          supply_register_at_address (regcache, current_regnum,
+                                      current_address);
+        }
+    }
+}
+
+/* to_prepare_to_store when inferior_ptid is different from the running
+   thread.  */
+
+static void
+ravenscar_sparc_prepare_to_store (struct regcache *regcache)
+{
+  /* Nothing to do.  */
+}
+
+/* to_store_registers when inferior_ptid is different from the running
+   thread.  */
+
+static void
+ravenscar_sparc_store_registers (struct regcache *regcache, int regnum)
+{
+  struct gdbarch *gdbarch = get_regcache_arch (regcache);
+  int buf_size = register_size (gdbarch, regnum);
+  char buf [buf_size];
+  ULONGEST register_address;
+
+  if (register_in_thread_descriptor_p (regnum))
+    register_address =
+      ptid_get_tid (inferior_ptid) + sparc_register_offsets [regnum];
+  else if (register_on_stack_p (regnum))
+    {
+      regcache_cooked_read_unsigned (regcache, SPARC_SP_REGNUM,
+                                     &register_address);
+      register_address += sparc_register_offsets [regnum];
+    }
+  else
+    return;
+
+  regcache_raw_collect (regcache, regnum, buf);
+  write_memory (register_address,
+                buf,
+                buf_size);
+}
+
+void
+_initialize_ravenscar_sparc (void)
+{
+  ravenscar_sparc_ops.to_fetch_registers = ravenscar_sparc_fetch_registers;
+  ravenscar_sparc_ops.to_store_registers = ravenscar_sparc_store_registers;
+  ravenscar_sparc_ops.to_prepare_to_store = ravenscar_sparc_prepare_to_store;
+  ravenscar_register_arch_ops (&ravenscar_sparc_ops);
+}
diff --git a/gdb/ravenscar-thread.c b/gdb/ravenscar-thread.c
new file mode 100644
index 0000000..7a80dcf
--- /dev/null
+++ b/gdb/ravenscar-thread.c
@@ -0,0 +1,434 @@
+/* Ada Ravenscar thread support.
+
+   Copyright 2004, 2009, 2010 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[] = "running_thread";
+
+static const char known_tasks_name[] = "system__tasking__debug__known_tasks";
+
+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 CORE_ADDR read_thread_id (const char *symbol_name);
+
+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);
+}
+
+/* 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_running_thread =
+    lookup_minimal_symbol (running_thread_name, NULL, NULL);
+
+  return (msym_ravenscar_runtime_initializer
+	  && msym_known_tasks
+	  && 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)));
+}
+
+/* Read the thread ID whose symbol name is SYMBOL_NAME.  */
+
+static CORE_ADDR
+read_thread_id (const char *symbol_name)
+{
+  const struct minimal_symbol *object_msym =
+    lookup_minimal_symbol (symbol_name, NULL, NULL);
+  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 (0);
+
+  /* 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 = read_thread_id (running_thread_name);
+
+  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"));
+  else
+    fprintf_filtered (file, _("\
+Support for Ravenscar task/thread switching is disabled"));
+}
+
+/* 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, "set 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);
+}
diff --git a/gdb/ravenscar-thread.h b/gdb/ravenscar-thread.h
new file mode 100644
index 0000000..c8844e3
--- /dev/null
+++ b/gdb/ravenscar-thread.h
@@ -0,0 +1,41 @@
+/* Ada Ravenscar thread support.
+
+   Copyright 2004, 2010 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/>.  */
+
+#ifndef RAVENSCAR_THREAD_H
+#define RAVENSCAR_THREAD_H
+
+/* Architecture-specific hooks.  */
+
+struct ravenscar_arch_ops
+{
+  void (*to_fetch_registers) (struct regcache *, int);
+  void (*to_store_registers) (struct regcache *, int);
+  void (*to_prepare_to_store) (struct regcache *);
+};
+
+/* Register implementations for target ops to_store_registers,
+   to_prepare_to_store and to_fetch_registers when the inferior_ptid
+   is different from the running thread.  In that case, the registers
+   are saved in a architecture-specific location.  */
+/* FIXME: only one architecture can be registered for now. See
+   implementation.  */
+
+extern void ravenscar_register_arch_ops (struct ravenscar_arch_ops *ops);
+
+#endif /* !defined (RAVENSCAR_THREAD_H) */