gdb/xml-tdesc.c

   1 /* XML target description support for GDB.
   2
   3    Copyright (C) 2006, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
   4
   5    Contributed by CodeSourcery.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23 #include "target.h"
  24 #include "target-descriptions.h"
  25 #include "xml-support.h"
  26 #include "xml-tdesc.h"
  27 #include "osabi.h"
  28
  29 #include "filenames.h"
  30
  31 #include "gdb_assert.h"
  32
  33 #if !defined(HAVE_LIBEXPAT)
  34
  35 /* Parse DOCUMENT into a target description.  Or don't, since we don't have
  36    an XML parser.  */
  37
  38 static struct target_desc *
  39 tdesc_parse_xml (const char *document, xml_fetch_another fetcher,
  40                  void *fetcher_baton)
  41 {
  42   static int have_warned;
  43
  44   if (!have_warned)
  45     {
  46       have_warned = 1;
  47       warning (_("Can not parse XML target description; XML support was "
  48                  "disabled at compile time"));
  49     }
  50
  51   return NULL;
  52 }
  53
  54 #else /* HAVE_LIBEXPAT */
  55
  56 /* A record of every XML description we have parsed.  We never discard
  57    old descriptions, because we never discard gdbarches.  As long as we
  58    have a gdbarch referencing this description, we want to have a copy
  59    of it here, so that if we parse the same XML document again we can
  60    return the same "struct target_desc *"; if they are not singletons,
  61    then we will create unnecessary duplicate gdbarches.  See
  62    gdbarch_list_lookup_by_info.  */
  63
  64 struct tdesc_xml_cache
  65 {
  66   const char *xml_document;
  67   struct target_desc *tdesc;
  68 };
  69 typedef struct tdesc_xml_cache tdesc_xml_cache_s;
  70 DEF_VEC_O(tdesc_xml_cache_s);
  71
  72 static VEC(tdesc_xml_cache_s) *xml_cache;
  73
  74 /* Callback data for target description parsing.  */
  75
  76 struct tdesc_parsing_data
  77 {
  78   /* The target description we are building.  */
  79   struct target_desc *tdesc;
  80
  81   /* The target feature we are currently parsing, or last parsed.  */
  82   struct tdesc_feature *current_feature;
  83
  84   /* The register number to use for the next register we see, if
  85      it does not have its own.  This starts at zero.  */
  86   int next_regnum;
  87
  88   /* The struct or union we are currently parsing, or last parsed.  */
  89   struct tdesc_type *current_type;
  90
  91   /* The byte size of the current struct type, if specified.  Zero
  92      if not specified.  */
  93   int current_type_size;
  94
  95   /* Whether the current type is a flags type.  */
  96   int current_type_is_flags;
  97 };
  98
  99 /* Handle the end of an <architecture> element and its value.  */
 100
 101 static void
 102 tdesc_end_arch (struct gdb_xml_parser *parser,
 103                 const struct gdb_xml_element *element,
 104                 void *user_data, const char *body_text)
 105 {
 106   struct tdesc_parsing_data *data = user_data;
 107   const struct bfd_arch_info *arch;
 108
 109   arch = bfd_scan_arch (body_text);
 110   if (arch == NULL)
 111     gdb_xml_error (parser, _("Target description specified unknown "
 112                              "architecture \"%s\""), body_text);
 113   set_tdesc_architecture (data->tdesc, arch);
 114 }
 115
 116 /* Handle the end of an <osabi> element and its value.  */
 117
 118 static void
 119 tdesc_end_osabi (struct gdb_xml_parser *parser,
 120                  const struct gdb_xml_element *element,
 121                  void *user_data, const char *body_text)
 122 {
 123   struct tdesc_parsing_data *data = user_data;
 124   enum gdb_osabi osabi;
 125
 126   osabi = osabi_from_tdesc_string (body_text);
 127   if (osabi == GDB_OSABI_UNKNOWN)
 128     warning (_("Target description specified unknown osabi \"%s\""),
 129              body_text);
 130   else
 131     set_tdesc_osabi (data->tdesc, osabi);
 132 }
 133
 134 /* Handle the end of a <compatible> element and its value.  */
 135
 136 static void
 137 tdesc_end_compatible (struct gdb_xml_parser *parser,
 138                       const struct gdb_xml_element *element,
 139                       void *user_data, const char *body_text)
 140 {
 141   struct tdesc_parsing_data *data = user_data;
 142   const struct bfd_arch_info *arch;
 143
 144   arch = bfd_scan_arch (body_text);
 145   tdesc_add_compatible (data->tdesc, arch);
 146 }
 147
 148 /* Handle the start of a <target> element.  */
 149
 150 static void
 151 tdesc_start_target (struct gdb_xml_parser *parser,
 152                     const struct gdb_xml_element *element,
 153                     void *user_data, VEC(gdb_xml_value_s) *attributes)
 154 {
 155   char *version = VEC_index (gdb_xml_value_s, attributes, 0)->value;
 156
 157   if (strcmp (version, "1.0") != 0)
 158     gdb_xml_error (parser,
 159                    _("Target description has unsupported version \"%s\""),
 160                    version);
 161 }
 162
 163 /* Handle the start of a <feature> element.  */
 164
 165 static void
 166 tdesc_start_feature (struct gdb_xml_parser *parser,
 167                      const struct gdb_xml_element *element,
 168                      void *user_data, VEC(gdb_xml_value_s) *attributes)
 169 {
 170   struct tdesc_parsing_data *data = user_data;
 171   char *name = VEC_index (gdb_xml_value_s, attributes, 0)->value;
 172
 173   data->current_feature = tdesc_create_feature (data->tdesc, name);
 174 }
 175
 176 /* Handle the start of a <reg> element.  Fill in the optional
 177    attributes and attach it to the containing feature.  */
 178
 179 static void
 180 tdesc_start_reg (struct gdb_xml_parser *parser,
 181                  const struct gdb_xml_element *element,
 182                  void *user_data, VEC(gdb_xml_value_s) *attributes)
 183 {
 184   struct tdesc_parsing_data *data = user_data;
 185   struct gdb_xml_value *attrs = VEC_address (gdb_xml_value_s, attributes);
 186   int ix = 0, length;
 187   char *name, *group, *type;
 188   int bitsize, regnum, save_restore;
 189
 190   length = VEC_length (gdb_xml_value_s, attributes);
 191
 192   name = attrs[ix++].value;
 193   bitsize = * (ULONGEST *) attrs[ix++].value;
 194
 195   if (ix < length && strcmp (attrs[ix].name, "regnum") == 0)
 196     regnum = * (ULONGEST *) attrs[ix++].value;
 197   else
 198     regnum = data->next_regnum;
 199
 200   if (ix < length && strcmp (attrs[ix].name, "type") == 0)
 201     type = attrs[ix++].value;
 202   else
 203     type = "int";
 204
 205   if (ix < length && strcmp (attrs[ix].name, "group") == 0)
 206     group = attrs[ix++].value;
 207   else
 208     group = NULL;
 209
 210   if (ix < length && strcmp (attrs[ix].name, "save-restore") == 0)
 211     save_restore = * (ULONGEST *) attrs[ix++].value;
 212   else
 213     save_restore = 1;
 214
 215   if (strcmp (type, "int") != 0
 216       && strcmp (type, "float") != 0
 217       && tdesc_named_type (data->current_feature, type) == NULL)
 218     gdb_xml_error (parser, _("Register \"%s\" has unknown type \"%s\""),
 219                    name, type);
 220
 221   tdesc_create_reg (data->current_feature, name, regnum, save_restore, group,
 222                     bitsize, type);
 223
 224   data->next_regnum = regnum + 1;
 225 }
 226
 227 /* Handle the start of a <union> element.  Initialize the type and
 228    record it with the current feature.  */
 229
 230 static void
 231 tdesc_start_union (struct gdb_xml_parser *parser,
 232                    const struct gdb_xml_element *element,
 233                    void *user_data, VEC(gdb_xml_value_s) *attributes)
 234 {
 235   struct tdesc_parsing_data *data = user_data;
 236   char *id = VEC_index (gdb_xml_value_s, attributes, 0)->value;
 237
 238   data->current_type = tdesc_create_union (data->current_feature, id);
 239   data->current_type_size = 0;
 240   data->current_type_is_flags = 0;
 241 }
 242
 243 /* Handle the start of a <struct> element.  Initialize the type and
 244    record it with the current feature.  */
 245
 246 static void
 247 tdesc_start_struct (struct gdb_xml_parser *parser,
 248                    const struct gdb_xml_element *element,
 249                    void *user_data, VEC(gdb_xml_value_s) *attributes)
 250 {
 251   struct tdesc_parsing_data *data = user_data;
 252   char *id = VEC_index (gdb_xml_value_s, attributes, 0)->value;
 253   struct tdesc_type *type;
 254
 255   type = tdesc_create_struct (data->current_feature, id);
 256   data->current_type = type;
 257   data->current_type_size = 0;
 258   data->current_type_is_flags = 0;
 259
 260   if (VEC_length (gdb_xml_value_s, attributes) > 1)
 261     {
 262       int size = (int) * (ULONGEST *)
 263         VEC_index (gdb_xml_value_s, attributes, 1)->value;
 264
 265       tdesc_set_struct_size (type, size);
 266       data->current_type_size = size;
 267     }
 268 }
 269
 270 static void
 271 tdesc_start_flags (struct gdb_xml_parser *parser,
 272                    const struct gdb_xml_element *element,
 273                    void *user_data, VEC(gdb_xml_value_s) *attributes)
 274 {
 275   struct tdesc_parsing_data *data = user_data;
 276   char *id = VEC_index (gdb_xml_value_s, attributes, 0)->value;
 277   int length = (int) * (ULONGEST *)
 278     VEC_index (gdb_xml_value_s, attributes, 1)->value;
 279   struct tdesc_type *type;
 280
 281   type = tdesc_create_flags (data->current_feature, id, length);
 282
 283   data->current_type = type;
 284   data->current_type_size = 0;
 285   data->current_type_is_flags = 1;
 286 }
 287
 288 /* Handle the start of a <field> element.  Attach the field to the
 289    current struct or union.  */
 290
 291 static void
 292 tdesc_start_field (struct gdb_xml_parser *parser,
 293                    const struct gdb_xml_element *element,
 294                    void *user_data, VEC(gdb_xml_value_s) *attributes)
 295 {
 296   struct tdesc_parsing_data *data = user_data;
 297   int ix = 0, length;
 298   struct gdb_xml_value *attrs = VEC_address (gdb_xml_value_s, attributes);
 299   struct tdesc_type *field_type;
 300   char *field_name, *field_type_id;
 301   int start, end;
 302
 303   length = VEC_length (gdb_xml_value_s, attributes);
 304
 305   field_name = attrs[ix++].value;
 306
 307   if (ix < length && strcmp (attrs[ix].name, "type") == 0)
 308     field_type_id = attrs[ix++].value;
 309   else
 310     field_type_id = NULL;
 311
 312   if (ix < length && strcmp (attrs[ix].name, "start") == 0)
 313     start = * (ULONGEST *) attrs[ix++].value;
 314   else
 315     start = -1;
 316
 317   if (ix < length && strcmp (attrs[ix].name, "end") == 0)
 318     end = * (ULONGEST *) attrs[ix++].value;
 319   else
 320     end = -1;
 321
 322   if (field_type_id != NULL)
 323     {
 324       if (data->current_type_is_flags)
 325         gdb_xml_error (parser, _("Cannot add typed field \"%s\" to flags"),
 326                        field_name);
 327       if (data->current_type_size != 0)
 328         gdb_xml_error (parser,
 329                        _("Explicitly sized type can not "
 330                          "contain non-bitfield \"%s\""),
 331                        field_name);
 332
 333       field_type = tdesc_named_type (data->current_feature, field_type_id);
 334       if (field_type == NULL)
 335         gdb_xml_error (parser, _("Field \"%s\" references undefined "
 336                                  "type \"%s\""),
 337                        field_name, field_type_id);
 338
 339       tdesc_add_field (data->current_type, field_name, field_type);
 340     }
 341   else if (start != -1 && end != -1)
 342     {
 343       struct tdesc_type *t = data->current_type;
 344
 345       if (data->current_type_is_flags)
 346         tdesc_add_flag (t, start, field_name);
 347       else
 348         {
 349           if (data->current_type_size == 0)
 350             gdb_xml_error (parser,
 351                            _("Implicitly sized type can "
 352                              "not contain bitfield \"%s\""),
 353                            field_name);
 354
 355           if (end >= 64)
 356             gdb_xml_error (parser,
 357                            _("Bitfield \"%s\" goes past "
 358                              "64 bits (unsupported)"),
 359                            field_name);
 360
 361           /* Assume that the bit numbering in XML is "lsb-zero".  Most
 362              architectures other than PowerPC use this ordering.  In
 363              the future, we can add an XML tag to indicate "msb-zero"
 364              numbering.  */
 365           if (start > end)
 366             gdb_xml_error (parser, _("Bitfield \"%s\" has start after end"),
 367                            field_name);
 368
 369           if (end >= data->current_type_size * TARGET_CHAR_BIT)
 370             gdb_xml_error (parser,
 371                            _("Bitfield \"%s\" does not fit in struct"));
 372
 373           tdesc_add_bitfield (t, field_name, start, end);
 374         }
 375     }
 376   else
 377     gdb_xml_error (parser, _("Field \"%s\" has neither type nor bit position"),
 378                    field_name);
 379 }
 380
 381 /* Handle the start of a <vector> element.  Initialize the type and
 382    record it with the current feature.  */
 383
 384 static void
 385 tdesc_start_vector (struct gdb_xml_parser *parser,
 386                     const struct gdb_xml_element *element,
 387                     void *user_data, VEC(gdb_xml_value_s) *attributes)
 388 {
 389   struct tdesc_parsing_data *data = user_data;
 390   struct gdb_xml_value *attrs = VEC_address (gdb_xml_value_s, attributes);
 391   struct tdesc_type *field_type;
 392   char *id, *field_type_id;
 393   int count;
 394
 395   id = attrs[0].value;
 396   field_type_id = attrs[1].value;
 397   count = * (ULONGEST *) attrs[2].value;
 398
 399   field_type = tdesc_named_type (data->current_feature, field_type_id);
 400   if (field_type == NULL)
 401     gdb_xml_error (parser, _("Vector \"%s\" references undefined type \"%s\""),
 402                    id, field_type_id);
 403
 404   tdesc_create_vector (data->current_feature, id, field_type, count);
 405 }
 406
 407 /* The elements and attributes of an XML target description.  */
 408
 409 static const struct gdb_xml_attribute field_attributes[] = {
 410   { "name", GDB_XML_AF_NONE, NULL, NULL },
 411   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 412   { "start", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 413   { "end", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 414   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 415 };
 416
 417 static const struct gdb_xml_element struct_union_children[] = {
 418   { "field", field_attributes, NULL, GDB_XML_EF_REPEATABLE,
 419     tdesc_start_field, NULL },
 420   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 421 };
 422
 423 static const struct gdb_xml_attribute reg_attributes[] = {
 424   { "name", GDB_XML_AF_NONE, NULL, NULL },
 425   { "bitsize", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 426   { "regnum", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 427   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 428   { "group", GDB_XML_AF_OPTIONAL, NULL, NULL },
 429   { "save-restore", GDB_XML_AF_OPTIONAL,
 430     gdb_xml_parse_attr_enum, gdb_xml_enums_boolean },
 431   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 432 };
 433
 434 static const struct gdb_xml_attribute struct_union_attributes[] = {
 435   { "id", GDB_XML_AF_NONE, NULL, NULL },
 436   { "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL},
 437   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 438 };
 439
 440 static const struct gdb_xml_attribute flags_attributes[] = {
 441   { "id", GDB_XML_AF_NONE, NULL, NULL },
 442   { "size", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL},
 443   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 444 };
 445
 446 static const struct gdb_xml_attribute vector_attributes[] = {
 447   { "id", GDB_XML_AF_NONE, NULL, NULL },
 448   { "type", GDB_XML_AF_NONE, NULL, NULL },
 449   { "count", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 450   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 451 };
 452
 453 static const struct gdb_xml_attribute feature_attributes[] = {
 454   { "name", GDB_XML_AF_NONE, NULL, NULL },
 455   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 456 };
 457
 458 static const struct gdb_xml_element feature_children[] = {
 459   { "reg", reg_attributes, NULL,
 460     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 461     tdesc_start_reg, NULL },
 462   { "struct", struct_union_attributes, struct_union_children,
 463     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 464     tdesc_start_struct, NULL },
 465   { "union", struct_union_attributes, struct_union_children,
 466     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 467     tdesc_start_union, NULL },
 468   { "flags", flags_attributes, struct_union_children,
 469     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 470     tdesc_start_flags, NULL },
 471   { "vector", vector_attributes, NULL,
 472     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 473     tdesc_start_vector, NULL },
 474   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 475 };
 476
 477 static const struct gdb_xml_attribute target_attributes[] = {
 478   { "version", GDB_XML_AF_NONE, NULL, NULL },
 479   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 480 };
 481
 482 static const struct gdb_xml_element target_children[] = {
 483   { "architecture", NULL, NULL, GDB_XML_EF_OPTIONAL,
 484     NULL, tdesc_end_arch },
 485   { "osabi", NULL, NULL, GDB_XML_EF_OPTIONAL,
 486     NULL, tdesc_end_osabi },
 487   { "compatible", NULL, NULL, GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 488     NULL, tdesc_end_compatible },
 489   { "feature", feature_attributes, feature_children,
 490     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 491     tdesc_start_feature, NULL },
 492   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 493 };
 494
 495 static const struct gdb_xml_element tdesc_elements[] = {
 496   { "target", target_attributes, target_children, GDB_XML_EF_NONE,
 497     tdesc_start_target, NULL },
 498   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 499 };
 500
 501 /* Parse DOCUMENT into a target description and return it.  */
 502
 503 static struct target_desc *
 504 tdesc_parse_xml (const char *document, xml_fetch_another fetcher,
 505                  void *fetcher_baton)
 506 {
 507   struct cleanup *back_to, *result_cleanup;
 508   struct tdesc_parsing_data data;
 509   struct tdesc_xml_cache *cache;
 510   char *expanded_text;
 511   int ix;
 512
 513   /* Expand all XInclude directives.  */
 514   expanded_text = xml_process_xincludes (_("target description"),
 515                                          document, fetcher, fetcher_baton, 0);
 516   if (expanded_text == NULL)
 517     {
 518       warning (_("Could not load XML target description; ignoring"));
 519       return NULL;
 520     }
 521
 522   /* Check for an exact match in the list of descriptions we have
 523      previously parsed.  strcmp is a slightly inefficient way to
 524      do this; an SHA-1 checksum would work as well.  */
 525   for (ix = 0; VEC_iterate (tdesc_xml_cache_s, xml_cache, ix, cache); ix++)
 526     if (strcmp (cache->xml_document, expanded_text) == 0)
 527       {
 528        xfree (expanded_text);
 529        return cache->tdesc;
 530       }
 531
 532   back_to = make_cleanup (null_cleanup, NULL);
 533
 534   memset (&data, 0, sizeof (struct tdesc_parsing_data));
 535   data.tdesc = allocate_target_description ();
 536   result_cleanup = make_cleanup_free_target_description (data.tdesc);
 537   make_cleanup (xfree, expanded_text);
 538
 539   if (gdb_xml_parse_quick (_("target description"), "gdb-target.dtd",
 540                            tdesc_elements, expanded_text, &data) == 0)
 541     {
 542       /* Parsed successfully.  */
 543       struct tdesc_xml_cache new_cache;
 544
 545       new_cache.xml_document = expanded_text;
 546       new_cache.tdesc = data.tdesc;
 547       VEC_safe_push (tdesc_xml_cache_s, xml_cache, &new_cache);
 548       discard_cleanups (result_cleanup);
 549       do_cleanups (back_to);
 550       return data.tdesc;
 551     }
 552   else
 553     {
 554       warning (_("Could not load XML target description; ignoring"));
 555       do_cleanups (back_to);
 556       return NULL;
 557     }
 558 }
 559 #endif /* HAVE_LIBEXPAT */
 560 \f
 561
 562 /* Read an XML target description from FILENAME.  Parse it, and return
 563    the parsed description.  */
 564
 565 const struct target_desc *
 566 file_read_description_xml (const char *filename)
 567 {
 568   struct target_desc *tdesc;
 569   char *tdesc_str;
 570   struct cleanup *back_to;
 571   char *dirname;
 572
 573   tdesc_str = xml_fetch_content_from_file (filename, NULL);
 574   if (tdesc_str == NULL)
 575     {
 576       warning (_("Could not open \"%s\""), filename);
 577       return NULL;
 578     }
 579
 580   back_to = make_cleanup (xfree, tdesc_str);
 581
 582   dirname = ldirname (filename);
 583   if (dirname != NULL)
 584     make_cleanup (xfree, dirname);
 585
 586   tdesc = tdesc_parse_xml (tdesc_str, xml_fetch_content_from_file, dirname);
 587   do_cleanups (back_to);
 588
 589   return tdesc;
 590 }
 591
 592 /* Read a string representation of available features from the target,
 593    using TARGET_OBJECT_AVAILABLE_FEATURES.  The returned string is
 594    malloc allocated and NUL-terminated.  NAME should be a non-NULL
 595    string identifying the XML document we want; the top level document
 596    is "target.xml".  Other calls may be performed for the DTD or
 597    for <xi:include>.  */
 598
 599 static char *
 600 fetch_available_features_from_target (const char *name, void *baton_)
 601 {
 602   struct target_ops *ops = baton_;
 603
 604   /* Read this object as a string.  This ensures that a NUL
 605      terminator is added.  */
 606   return target_read_stralloc (ops,
 607                                TARGET_OBJECT_AVAILABLE_FEATURES,
 608                                name);
 609 }
 610 \f
 611
 612 /* Read an XML target description using OPS.  Parse it, and return the
 613    parsed description.  */
 614
 615 const struct target_desc *
 616 target_read_description_xml (struct target_ops *ops)
 617 {
 618   struct target_desc *tdesc;
 619   char *tdesc_str;
 620   struct cleanup *back_to;
 621
 622   tdesc_str = fetch_available_features_from_target ("target.xml", ops);
 623   if (tdesc_str == NULL)
 624     return NULL;
 625
 626   back_to = make_cleanup (xfree, tdesc_str);
 627   tdesc = tdesc_parse_xml (tdesc_str,
 628                            fetch_available_features_from_target,
 629                            ops);
 630   do_cleanups (back_to);
 631
 632   return tdesc;
 633 }