XML feature description support.

	* NEWS: Mention target descriptions, "set tdesc filename",
	"unset tdesc filename", "show tdesc filename", and
	qXfer:features:read.
	* arch-utils.c (choose_architecture_for_target): New function.
	(gdbarch_info_fill): Call it.
	* target-descriptions.c (struct property): Make members non-const.
	(struct target_desc): Add arch member.
	(target_description_filename): New variable.
	(target_find_description): Try via XML first.
	(tdesc_architecture): New.
	(free_target_description, make_cleanup_free_target_description): New.
	(set_tdesc_property): Call xstrdup.
	(set_tdesc_architecture, tdesc_set_cmdlist, tdesc_show_cmdlist)
	(tdesc_unset_cmdlist, unset_tdesc_cmd, unset_tdesc_filename_cmd)
	(set_tdesc_cmd, show_tdesc_cmd, set_tdesc_filename_cmd)
	(show_tdesc_filename_cmd, _initialize_target_descriptions): New.
	* target-descriptions.h (tdesc_architecture)
	(make_cleanup_free_target_description, set_tdesc_architecture): New
	prototypes.
	* Makefile.in (SFILES): Add xml-tdesc.c.
	(COMMON_OBS): Add xml-tdesc.o.
	(target-descriptions.o): Update.
	(xml-tdesc.o): New rule.
	* xml-tdesc.c, xml-tdesc.h: New files.
	* remote.c (PACKET_qXfer_features): New enum.
	(remote_protocol_features): Add qXfer:features:read.
	(remote_xfer_partial): Handle TARGET_OBJECT_AVAILABLE_FEATURES.
	(_initialize_remote): Register qXfer:features:read.
	* target.h (enum target_object): Add TARGET_OBJECT_AVAILABLE_FEATURES.
	* features/gdb-target.dtd: New file.

	* linux-i386-low.c (the_low_target): Set arch_string.
	* linux-x86-64-low.c (the_low_target): Likewise.
	* linux-low.c (linux_arch_string): New.
	(linux_target_ops): Add it.
	* linux-low.h (struct linux_target_ops): Add arch_string.
	* server.c (write_qxfer_response): Use const void * for DATA.
	(get_features_xml): New.
	(handle_query): Handle qXfer:features:read.  Report it for qSupported.
	* target.h (struct target_ops): Add arch_string method.

	* gdb.texinfo (Target Descriptions): New section.
	(General Query Packets): Add QPassSignals anchor.  Mention
	qXfer:features:read under qSupported.  Expand mentions of
	qXfer:memory-map:read and QPassSignals.  Document
	qXfer:features:read.

1 files changed, 164 insertions, 5 deletions

diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 9699b7d47c9..1100f5ebaf3 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -23,9 +23,11 @@
 
 #include "defs.h"
 #include "arch-utils.h"
+#include "gdbcmd.h"
 #include "target.h"
 #include "target-descriptions.h"
 #include "vec.h"
+#include "xml-tdesc.h"
 
 #include "gdb_assert.h"
 
@@ -33,13 +35,16 @@
 
 typedef struct property
 {
-  const char *key;
-  const char *value;
+  char *key;
+  char *value;
 } property_s;
 DEF_VEC_O(property_s);
 
 struct target_desc
 {
+  /* The architecture reported by the target, if any.  */
+  const struct bfd_arch_info *arch;
+
   /* Any architecture-specific properties specified by the target.  */
   VEC(property_s) *properties;
 };
@@ -61,6 +66,12 @@ static int target_desc_fetched;
 
 static const struct target_desc *current_target_desc;
 
+/* Other global variables.  */
+
+/* The filename to read a target description from.  */
+
+static char *target_description_filename;
+
 /* Fetch the current target's description, and switch the current
    architecture to one which incorporates that description.  */
 
@@ -79,7 +90,22 @@ target_find_description (void)
      disconnected from the previous target.  */
   gdb_assert (gdbarch_target_desc (current_gdbarch) == NULL);
 
-  current_target_desc = target_read_description (&current_target);
+  /* First try to fetch an XML description from the user-specified
+     file.  */
+  current_target_desc = NULL;
+  if (target_description_filename != NULL
+      && *target_description_filename != '\0')
+    current_target_desc
+      = file_read_description_xml (target_description_filename);
+
+  /* Next try to read the description from the current target using
+     target objects.  */
+  if (current_target_desc == NULL)
+    current_target_desc = target_read_description_xml (&current_target);
+
+  /* If that failed try a target-specific hook.  */
+  if (current_target_desc == NULL)
+    current_target_desc = target_read_description (&current_target);
 
   /* If a non-NULL description was returned, then update the current
      architecture.  */
@@ -130,6 +156,9 @@ target_current_description (void)
 
   return NULL;
 }
+
+
+/* Direct accessors for feature sets.  */
 
 /* Return the string value of a property named KEY, or NULL if the
    property was not specified.  */
@@ -148,6 +177,16 @@ tdesc_property (const struct target_desc *target_desc, const char *key)
   return NULL;
 }
 
+/* Return the BFD architecture associated with this target
+   description, or NULL if no architecture was specified.  */
+
+const struct bfd_arch_info *
+tdesc_architecture (const struct target_desc *target_desc)
+{
+  return target_desc->arch;
+}
+
+
 /* Methods for constructing a target description.  */
 
 struct target_desc *
@@ -156,6 +195,31 @@ allocate_target_description (void)
   return XZALLOC (struct target_desc);
 }
 
+static void
+free_target_description (void *arg)
+{
+  struct target_desc *target_desc = arg;
+  struct property *prop;
+  int ix;
+
+  for (ix = 0;
+       VEC_iterate (property_s, target_desc->properties, ix, prop);
+       ix++)
+    {
+      xfree (prop->key);
+      xfree (prop->value);
+    }
+  VEC_free (property_s, target_desc->properties);
+
+  xfree (target_desc);
+}
+
+struct cleanup *
+make_cleanup_free_target_description (struct target_desc *target_desc)
+{
+  return make_cleanup (free_target_description, target_desc);
+}
+
 void
 set_tdesc_property (struct target_desc *target_desc,
 		    const char *key, const char *value)
@@ -171,7 +235,102 @@ set_tdesc_property (struct target_desc *target_desc,
       internal_error (__FILE__, __LINE__,
 		      _("Attempted to add duplicate property \"%s\""), key);
 
-  new_prop.key = key;
-  new_prop.value = value;
+  new_prop.key = xstrdup (key);
+  new_prop.value = xstrdup (value);
   VEC_safe_push (property_s, target_desc->properties, &new_prop);
 }
+
+void
+set_tdesc_architecture (struct target_desc *target_desc,
+			const struct bfd_arch_info *arch)
+{
+  target_desc->arch = arch;
+}
+
+
+static struct cmd_list_element *tdesc_set_cmdlist, *tdesc_show_cmdlist;
+static struct cmd_list_element *tdesc_unset_cmdlist;
+
+/* Helper functions for the CLI commands.  */
+
+static void
+set_tdesc_cmd (char *args, int from_tty)
+{
+  help_list (tdesc_set_cmdlist, "set tdesc ", -1, gdb_stdout);
+}
+
+static void
+show_tdesc_cmd (char *args, int from_tty)
+{
+  cmd_show_list (tdesc_show_cmdlist, from_tty, "");
+}
+
+static void
+unset_tdesc_cmd (char *args, int from_tty)
+{
+  help_list (tdesc_unset_cmdlist, "unset tdesc ", -1, gdb_stdout);
+}
+
+static void
+set_tdesc_filename_cmd (char *args, int from_tty,
+			struct cmd_list_element *c)
+{
+  target_clear_description ();
+  target_find_description ();
+}
+
+static void
+show_tdesc_filename_cmd (struct ui_file *file, int from_tty,
+			 struct cmd_list_element *c,
+			 const char *value)
+{
+  if (value != NULL && *value != '\0')
+    printf_filtered (_("\
+The target description will be read from \"%s\".\n"),
+		     value);
+  else
+    printf_filtered (_("\
+The target description will be read from the target.\n"));
+}
+
+static void
+unset_tdesc_filename_cmd (char *args, int from_tty)
+{
+  xfree (target_description_filename);
+  target_description_filename = NULL;
+  target_clear_description ();
+  target_find_description ();
+}
+
+void
+_initialize_target_descriptions (void)
+{
+  add_prefix_cmd ("tdesc", class_maintenance, set_tdesc_cmd, _("\
+Set target description specific variables."),
+		  &tdesc_set_cmdlist, "set tdesc ",
+		  0 /* allow-unknown */, &setlist);
+  add_prefix_cmd ("tdesc", class_maintenance, show_tdesc_cmd, _("\
+Show target description specific variables."),
+		  &tdesc_show_cmdlist, "show tdesc ",
+		  0 /* allow-unknown */, &showlist);
+  add_prefix_cmd ("tdesc", class_maintenance, unset_tdesc_cmd, _("\
+Unset target description specific variables."),
+		  &tdesc_unset_cmdlist, "unset tdesc ",
+		  0 /* allow-unknown */, &unsetlist);
+
+  add_setshow_filename_cmd ("filename", class_obscure,
+			    &target_description_filename,
+			    _("\
+Set the file to read for an XML target description"), _("\
+Show the file to read for an XML target description"), _("\
+When set, GDB will read the target description from a local\n\
+file instead of querying the remote target."),
+			    set_tdesc_filename_cmd,
+			    show_tdesc_filename_cmd,
+			    &tdesc_set_cmdlist, &tdesc_show_cmdlist);
+
+  add_cmd ("filename", class_obscure, unset_tdesc_filename_cmd, _("\
+Unset the file to read for an XML target description.  When unset,\n\
+GDB will read the description from the target."),
+	   &tdesc_unset_cmdlist);
+}