gdb/xml-tdesc.c

   1 /* XML target description support for GDB.
   2
   3    Copyright (C) 2006-2024 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 "target.h"
  23 #include "target-descriptions.h"
  24 #include "xml-support.h"
  25 #include "xml-tdesc.h"
  26 #include "osabi.h"
  27 #include "filenames.h"
  28 #include <unordered_map>
  29 #include <string>
  30
  31 /* Maximum sizes.
  32    This is just to catch obviously wrong values.  */
  33 #define MAX_FIELD_SIZE 65536
  34 #define MAX_FIELD_BITSIZE (MAX_FIELD_SIZE * TARGET_CHAR_BIT)
  35 #define MAX_VECTOR_SIZE 65536
  36
  37 #if !defined(HAVE_LIBEXPAT)
  38
  39 /* Parse DOCUMENT into a target description.  Or don't, since we don't have
  40    an XML parser.  */
  41
  42 static struct target_desc *
  43 tdesc_parse_xml (const char *document, xml_fetch_another fetcher)
  44 {
  45   static int have_warned;
  46
  47   if (!have_warned)
  48     {
  49       have_warned = 1;
  50       warning (_("Can not parse XML target description; XML support was "
  51                  "disabled at compile time"));
  52     }
  53
  54   return NULL;
  55 }
  56
  57 #else /* HAVE_LIBEXPAT */
  58
  59 /* A record of every XML description we have parsed.  We never discard
  60    old descriptions, because we never discard gdbarches.  As long as we
  61    have a gdbarch referencing this description, we want to have a copy
  62    of it here, so that if we parse the same XML document again we can
  63    return the same "struct target_desc *"; if they are not singletons,
  64    then we will create unnecessary duplicate gdbarches.  See
  65    gdbarch_list_lookup_by_info.  */
  66
  67 static std::unordered_map<std::string, target_desc_up> xml_cache;
  68
  69 /* Callback data for target description parsing.  */
  70
  71 struct tdesc_parsing_data
  72 {
  73   /* The target description we are building.  */
  74   struct target_desc *tdesc;
  75
  76   /* The target feature we are currently parsing, or last parsed.  */
  77   struct tdesc_feature *current_feature;
  78
  79   /* The register number to use for the next register we see, if
  80      it does not have its own.  This starts at zero.  */
  81   int next_regnum;
  82
  83   /* The struct or union we are currently parsing, or last parsed.  */
  84   tdesc_type_with_fields *current_type;
  85
  86   /* The byte size of the current struct/flags type, if specified.  Zero
  87      if not specified.  Flags values must specify a size.  */
  88   int current_type_size;
  89 };
  90
  91 /* Handle the end of an <architecture> element and its value.  */
  92
  93 static void
  94 tdesc_end_arch (struct gdb_xml_parser *parser,
  95                 const struct gdb_xml_element *element,
  96                 void *user_data, const char *body_text)
  97 {
  98   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
  99   const struct bfd_arch_info *arch;
 100
 101   arch = bfd_scan_arch (body_text);
 102   if (arch == NULL)
 103     gdb_xml_error (parser, _("Target description specified unknown "
 104                              "architecture \"%s\""), body_text);
 105   set_tdesc_architecture (data->tdesc, arch);
 106 }
 107
 108 /* Handle the end of an <osabi> element and its value.  */
 109
 110 static void
 111 tdesc_end_osabi (struct gdb_xml_parser *parser,
 112                  const struct gdb_xml_element *element,
 113                  void *user_data, const char *body_text)
 114 {
 115   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 116   enum gdb_osabi osabi;
 117
 118   osabi = osabi_from_tdesc_string (body_text);
 119   if (osabi == GDB_OSABI_UNKNOWN)
 120     warning (_("Target description specified unknown osabi \"%s\""),
 121              body_text);
 122   else
 123     set_tdesc_osabi (data->tdesc, osabi);
 124 }
 125
 126 /* Handle the end of a <compatible> element and its value.  */
 127
 128 static void
 129 tdesc_end_compatible (struct gdb_xml_parser *parser,
 130                       const struct gdb_xml_element *element,
 131                       void *user_data, const char *body_text)
 132 {
 133   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 134   const struct bfd_arch_info *arch;
 135
 136   arch = bfd_scan_arch (body_text);
 137   tdesc_add_compatible (data->tdesc, arch);
 138 }
 139
 140 /* Handle the start of a <target> element.  */
 141
 142 static void
 143 tdesc_start_target (struct gdb_xml_parser *parser,
 144                     const struct gdb_xml_element *element,
 145                     void *user_data, std::vector<gdb_xml_value> &attributes)
 146 {
 147   char *version
 148     = (char *) xml_find_attribute (attributes, "version")->value.get ();
 149
 150   if (strcmp (version, "1.0") != 0)
 151     gdb_xml_error (parser,
 152                    _("Target description has unsupported version \"%s\""),
 153                    version);
 154 }
 155
 156 /* Handle the start of a <feature> element.  */
 157
 158 static void
 159 tdesc_start_feature (struct gdb_xml_parser *parser,
 160                      const struct gdb_xml_element *element,
 161                      void *user_data, std::vector<gdb_xml_value> &attributes)
 162 {
 163   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 164   char *name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 165
 166   data->current_feature = tdesc_create_feature (data->tdesc, name);
 167 }
 168
 169 /* Handle the start of a <reg> element.  Fill in the optional
 170    attributes and attach it to the containing feature.  */
 171
 172 static void
 173 tdesc_start_reg (struct gdb_xml_parser *parser,
 174                  const struct gdb_xml_element *element,
 175                  void *user_data, std::vector<gdb_xml_value> &attributes)
 176 {
 177   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 178   int ix = 0;
 179   char *name, *group;
 180   const char *type;
 181   int bitsize, regnum, save_restore;
 182
 183   int length = attributes.size ();
 184
 185   name = (char *) attributes[ix++].value.get ();
 186   bitsize = * (ULONGEST *) attributes[ix++].value.get ();
 187
 188   if (ix < length && strcmp (attributes[ix].name, "regnum") == 0)
 189     regnum = * (ULONGEST *) attributes[ix++].value.get ();
 190   else
 191     regnum = data->next_regnum;
 192
 193   if (ix < length && strcmp (attributes[ix].name, "type") == 0)
 194     type = (char *) attributes[ix++].value.get ();
 195   else
 196     type = "int";
 197
 198   if (ix < length && strcmp (attributes[ix].name, "group") == 0)
 199     group = (char *) attributes[ix++].value.get ();
 200   else
 201     group = NULL;
 202
 203   if (ix < length && strcmp (attributes[ix].name, "save-restore") == 0)
 204     save_restore = * (ULONGEST *) attributes[ix++].value.get ();
 205   else
 206     save_restore = 1;
 207
 208   if (strcmp (type, "int") != 0
 209       && strcmp (type, "float") != 0
 210       && tdesc_named_type (data->current_feature, type) == NULL)
 211     gdb_xml_error (parser, _("Register \"%s\" has unknown type \"%s\""),
 212                    name, type);
 213
 214   tdesc_create_reg (data->current_feature, name, regnum, save_restore, group,
 215                     bitsize, type);
 216
 217   data->next_regnum = regnum + 1;
 218 }
 219
 220 /* Handle the start of a <union> element.  Initialize the type and
 221    record it with the current feature.  */
 222
 223 static void
 224 tdesc_start_union (struct gdb_xml_parser *parser,
 225                    const struct gdb_xml_element *element,
 226                    void *user_data, std::vector<gdb_xml_value> &attributes)
 227 {
 228   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 229   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 230
 231   data->current_type = tdesc_create_union (data->current_feature, id);
 232   data->current_type_size = 0;
 233 }
 234
 235 /* Handle the start of a <struct> element.  Initialize the type and
 236    record it with the current feature.  */
 237
 238 static void
 239 tdesc_start_struct (struct gdb_xml_parser *parser,
 240                    const struct gdb_xml_element *element,
 241                    void *user_data, std::vector<gdb_xml_value> &attributes)
 242 {
 243   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 244   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 245   struct gdb_xml_value *attr;
 246
 247   tdesc_type_with_fields *type_with_fields
 248     = tdesc_create_struct (data->current_feature, id);
 249   data->current_type = type_with_fields;
 250   data->current_type_size = 0;
 251
 252   attr = xml_find_attribute (attributes, "size");
 253   if (attr != NULL)
 254     {
 255       ULONGEST size = * (ULONGEST *) attr->value.get ();
 256
 257       if (size > MAX_FIELD_SIZE)
 258         {
 259           gdb_xml_error (parser,
 260                          _("Struct size %s is larger than maximum (%d)"),
 261                          pulongest (size), MAX_FIELD_SIZE);
 262         }
 263       tdesc_set_struct_size (type_with_fields, size);
 264       data->current_type_size = size;
 265     }
 266 }
 267
 268 static void
 269 tdesc_start_flags (struct gdb_xml_parser *parser,
 270                    const struct gdb_xml_element *element,
 271                    void *user_data, std::vector<gdb_xml_value> &attributes)
 272 {
 273   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 274   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 275   ULONGEST size = * (ULONGEST *)
 276     xml_find_attribute (attributes, "size")->value.get ();
 277
 278   if (size > MAX_FIELD_SIZE)
 279     {
 280       gdb_xml_error (parser,
 281                      _("Flags size %s is larger than maximum (%d)"),
 282                      pulongest (size), MAX_FIELD_SIZE);
 283     }
 284
 285   data->current_type = tdesc_create_flags (data->current_feature, id, size);
 286   data->current_type_size = size;
 287 }
 288
 289 static void
 290 tdesc_start_enum (struct gdb_xml_parser *parser,
 291                   const struct gdb_xml_element *element,
 292                   void *user_data, std::vector<gdb_xml_value> &attributes)
 293 {
 294   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 295   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 296   int size = * (ULONGEST *)
 297     xml_find_attribute (attributes, "size")->value.get ();
 298
 299   if (size > MAX_FIELD_SIZE)
 300     {
 301       gdb_xml_error (parser,
 302                      _("Enum size %s is larger than maximum (%d)"),
 303                      pulongest (size), MAX_FIELD_SIZE);
 304     }
 305
 306   data->current_type = tdesc_create_enum (data->current_feature, id, size);
 307   data->current_type_size = 0;
 308 }
 309
 310 /* Handle the start of a <field> element.  Attach the field to the
 311    current struct, union or flags.  */
 312
 313 static void
 314 tdesc_start_field (struct gdb_xml_parser *parser,
 315                    const struct gdb_xml_element *element,
 316                    void *user_data, std::vector<gdb_xml_value> &attributes)
 317 {
 318   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 319   struct gdb_xml_value *attr;
 320   struct tdesc_type *field_type;
 321   char *field_name, *field_type_id;
 322   int start, end;
 323
 324   field_name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 325
 326   attr = xml_find_attribute (attributes, "type");
 327   if (attr != NULL)
 328     {
 329       field_type_id = (char *) attr->value.get ();
 330       field_type = tdesc_named_type (data->current_feature, field_type_id);
 331     }
 332   else
 333     {
 334       field_type_id = NULL;
 335       field_type = NULL;
 336     }
 337
 338   attr = xml_find_attribute (attributes, "start");
 339   if (attr != NULL)
 340     {
 341       ULONGEST ul_start = * (ULONGEST *) attr->value.get ();
 342
 343       if (ul_start > MAX_FIELD_BITSIZE)
 344         {
 345           gdb_xml_error (parser,
 346                          _("Field start %s is larger than maximum (%d)"),
 347                          pulongest (ul_start), MAX_FIELD_BITSIZE);
 348         }
 349       start = ul_start;
 350     }
 351   else
 352     start = -1;
 353
 354   attr = xml_find_attribute (attributes, "end");
 355   if (attr != NULL)
 356     {
 357       ULONGEST ul_end = * (ULONGEST *) attr->value.get ();
 358
 359       if (ul_end > MAX_FIELD_BITSIZE)
 360         {
 361           gdb_xml_error (parser,
 362                          _("Field end %s is larger than maximum (%d)"),
 363                          pulongest (ul_end), MAX_FIELD_BITSIZE);
 364         }
 365       end = ul_end;
 366     }
 367   else
 368     end = -1;
 369
 370   if (start != -1)
 371     {
 372       tdesc_type_with_fields *t = data->current_type;
 373
 374       /* Older versions of gdb can't handle elided end values.
 375          Stick with that for now, to help ensure backward compatibility.
 376          E.g., If a newer gdbserver is talking to an older gdb.  */
 377       if (end == -1)
 378         gdb_xml_error (parser, _("Missing end value"));
 379
 380       if (data->current_type_size == 0)
 381         gdb_xml_error (parser,
 382                        _("Bitfields must live in explicitly sized types"));
 383
 384       if (field_type_id != NULL
 385           && strcmp (field_type_id, "bool") == 0
 386           && start != end)
 387         {
 388           gdb_xml_error (parser,
 389                          _("Boolean fields must be one bit in size"));
 390         }
 391
 392       if (end >= 64)
 393         gdb_xml_error (parser,
 394                        _("Bitfield \"%s\" goes past "
 395                          "64 bits (unsupported)"),
 396                        field_name);
 397
 398       /* Assume that the bit numbering in XML is "lsb-zero".  Most
 399          architectures other than PowerPC use this ordering.  In the
 400          future, we can add an XML tag to indicate "msb-zero" numbering.  */
 401       if (start > end)
 402         gdb_xml_error (parser, _("Bitfield \"%s\" has start after end"),
 403                        field_name);
 404       if (end >= data->current_type_size * TARGET_CHAR_BIT)
 405         gdb_xml_error (parser, _("Bitfield \"%s\" does not fit in struct"),
 406                        field_name);
 407
 408       if (field_type != NULL)
 409         tdesc_add_typed_bitfield (t, field_name, start, end, field_type);
 410       else if (start == end)
 411         tdesc_add_flag (t, start, field_name);
 412       else
 413         tdesc_add_bitfield (t, field_name, start, end);
 414     }
 415   else if (start == -1 && end != -1)
 416     gdb_xml_error (parser, _("End specified but not start"));
 417   else if (field_type_id != NULL)
 418     {
 419       /* TDESC_TYPE_FLAGS values are explicitly sized, so the following test
 420          catches adding non-bitfield types to flags as well.  */
 421       if (data->current_type_size != 0)
 422         gdb_xml_error (parser,
 423                        _("Explicitly sized type cannot "
 424                          "contain non-bitfield \"%s\""),
 425                        field_name);
 426
 427       if (field_type == NULL)
 428         gdb_xml_error (parser, _("Field \"%s\" references undefined "
 429                                  "type \"%s\""),
 430                        field_name, field_type_id);
 431
 432       tdesc_add_field (data->current_type, field_name, field_type);
 433     }
 434   else
 435     gdb_xml_error (parser, _("Field \"%s\" has neither type nor bit position"),
 436                    field_name);
 437 }
 438
 439 /* Handle the start of an <evalue> element.  Attach the value to the
 440    current enum.  */
 441
 442 static void
 443 tdesc_start_enum_value (struct gdb_xml_parser *parser,
 444                         const struct gdb_xml_element *element,
 445                         void *user_data, std::vector<gdb_xml_value> &attributes)
 446 {
 447   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 448   struct gdb_xml_value *attr;
 449   char *field_name;
 450   ULONGEST ul_value;
 451   int value;
 452
 453   field_name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 454
 455   attr = xml_find_attribute (attributes, "value");
 456   ul_value = * (ULONGEST *) attr->value.get ();
 457   if (ul_value > INT_MAX)
 458     {
 459       gdb_xml_error (parser,
 460                      _("Enum value %s is larger than maximum (%d)"),
 461                      pulongest (ul_value), INT_MAX);
 462     }
 463   value = ul_value;
 464
 465   tdesc_add_enum_value (data->current_type, value, field_name);
 466 }
 467
 468 /* Handle the start of a <vector> element.  Initialize the type and
 469    record it with the current feature.  */
 470
 471 static void
 472 tdesc_start_vector (struct gdb_xml_parser *parser,
 473                     const struct gdb_xml_element *element,
 474                     void *user_data, std::vector<gdb_xml_value> &attributes)
 475 {
 476   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 477   struct tdesc_type *field_type;
 478   char *id, *field_type_id;
 479   ULONGEST count;
 480
 481   id = (char *) attributes[0].value.get ();
 482   field_type_id = (char *) attributes[1].value.get ();
 483   count = * (ULONGEST *) attributes[2].value.get ();
 484
 485   if (count > MAX_VECTOR_SIZE)
 486     {
 487       gdb_xml_error (parser,
 488                      _("Vector size %s is larger than maximum (%d)"),
 489                      pulongest (count), MAX_VECTOR_SIZE);
 490     }
 491
 492   field_type = tdesc_named_type (data->current_feature, field_type_id);
 493   if (field_type == NULL)
 494     gdb_xml_error (parser, _("Vector \"%s\" references undefined type \"%s\""),
 495                    id, field_type_id);
 496
 497   tdesc_create_vector (data->current_feature, id, field_type, count);
 498 }
 499
 500 /* The elements and attributes of an XML target description.  */
 501
 502 static const struct gdb_xml_attribute field_attributes[] = {
 503   { "name", GDB_XML_AF_NONE, NULL, NULL },
 504   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 505   { "start", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 506   { "end", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 507   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 508 };
 509
 510 static const struct gdb_xml_attribute enum_value_attributes[] = {
 511   { "name", GDB_XML_AF_NONE, NULL, NULL },
 512   { "value", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 513   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 514 };
 515
 516 static const struct gdb_xml_element struct_union_children[] = {
 517   { "field", field_attributes, NULL, GDB_XML_EF_REPEATABLE,
 518     tdesc_start_field, NULL },
 519   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 520 };
 521
 522 static const struct gdb_xml_element enum_children[] = {
 523   { "evalue", enum_value_attributes, NULL, GDB_XML_EF_REPEATABLE,
 524     tdesc_start_enum_value, NULL },
 525   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 526 };
 527
 528 static const struct gdb_xml_attribute reg_attributes[] = {
 529   { "name", GDB_XML_AF_NONE, NULL, NULL },
 530   { "bitsize", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 531   { "regnum", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 532   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 533   { "group", GDB_XML_AF_OPTIONAL, NULL, NULL },
 534   { "save-restore", GDB_XML_AF_OPTIONAL,
 535     gdb_xml_parse_attr_enum, gdb_xml_enums_boolean },
 536   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 537 };
 538
 539 static const struct gdb_xml_attribute struct_union_attributes[] = {
 540   { "id", GDB_XML_AF_NONE, NULL, NULL },
 541   { "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL},
 542   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 543 };
 544
 545 static const struct gdb_xml_attribute flags_attributes[] = {
 546   { "id", GDB_XML_AF_NONE, NULL, NULL },
 547   { "size", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL},
 548   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 549 };
 550
 551 static const struct gdb_xml_attribute enum_attributes[] = {
 552   { "id", GDB_XML_AF_NONE, NULL, NULL },
 553   { "size", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL},
 554   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 555 };
 556
 557 static const struct gdb_xml_attribute vector_attributes[] = {
 558   { "id", GDB_XML_AF_NONE, NULL, NULL },
 559   { "type", GDB_XML_AF_NONE, NULL, NULL },
 560   { "count", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 561   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 562 };
 563
 564 static const struct gdb_xml_attribute feature_attributes[] = {
 565   { "name", GDB_XML_AF_NONE, NULL, NULL },
 566   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 567 };
 568
 569 static const struct gdb_xml_element feature_children[] = {
 570   { "reg", reg_attributes, NULL,
 571     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 572     tdesc_start_reg, NULL },
 573   { "struct", struct_union_attributes, struct_union_children,
 574     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 575     tdesc_start_struct, NULL },
 576   { "union", struct_union_attributes, struct_union_children,
 577     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 578     tdesc_start_union, NULL },
 579   { "flags", flags_attributes, struct_union_children,
 580     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 581     tdesc_start_flags, NULL },
 582   { "enum", enum_attributes, enum_children,
 583     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 584     tdesc_start_enum, NULL },
 585   { "vector", vector_attributes, NULL,
 586     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 587     tdesc_start_vector, NULL },
 588   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 589 };
 590
 591 static const struct gdb_xml_attribute target_attributes[] = {
 592   { "version", GDB_XML_AF_NONE, NULL, NULL },
 593   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 594 };
 595
 596 static const struct gdb_xml_element target_children[] = {
 597   { "architecture", NULL, NULL, GDB_XML_EF_OPTIONAL,
 598     NULL, tdesc_end_arch },
 599   { "osabi", NULL, NULL, GDB_XML_EF_OPTIONAL,
 600     NULL, tdesc_end_osabi },
 601   { "compatible", NULL, NULL, GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 602     NULL, tdesc_end_compatible },
 603   { "feature", feature_attributes, feature_children,
 604     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 605     tdesc_start_feature, NULL },
 606   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 607 };
 608
 609 static const struct gdb_xml_element tdesc_elements[] = {
 610   { "target", target_attributes, target_children, GDB_XML_EF_NONE,
 611     tdesc_start_target, NULL },
 612   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 613 };
 614
 615 /* Parse DOCUMENT into a target description and return it.  */
 616
 617 static struct target_desc *
 618 tdesc_parse_xml (const char *document, xml_fetch_another fetcher)
 619 {
 620   struct tdesc_parsing_data data;
 621
 622   /* Expand all XInclude directives.  */
 623   std::string expanded_text;
 624
 625   if (!xml_process_xincludes (expanded_text,
 626                               _("target description"),
 627                               document, fetcher, 0))
 628     {
 629       warning (_("Could not load XML target description; ignoring"));
 630       return NULL;
 631     }
 632
 633   /* Check for an exact match in the list of descriptions we have
 634      previously parsed.  */
 635   const auto it = xml_cache.find (expanded_text);
 636   if (it != xml_cache.end ())
 637     return it->second.get ();
 638
 639   memset (&data, 0, sizeof (struct tdesc_parsing_data));
 640   target_desc_up description = allocate_target_description ();
 641   data.tdesc = description.get ();
 642
 643   if (gdb_xml_parse_quick (_("target description"), "gdb-target.dtd",
 644                            tdesc_elements, expanded_text.c_str (), &data) == 0)
 645     {
 646       /* Parsed successfully.  */
 647       xml_cache.emplace (std::move (expanded_text), std::move (description));
 648       return data.tdesc;
 649     }
 650   else
 651     {
 652       warning (_("Could not load XML target description; ignoring"));
 653       return NULL;
 654     }
 655 }
 656 #endif /* HAVE_LIBEXPAT */
 657 \f
 658
 659 /* Read an XML target description from FILENAME.  Parse it, and return
 660    the parsed description.  */
 661
 662 const struct target_desc *
 663 file_read_description_xml (const char *filename)
 664 {
 665   std::optional<gdb::char_vector> tdesc_str
 666     = xml_fetch_content_from_file (filename, NULL);
 667   if (!tdesc_str)
 668     {
 669       warning (_("Could not open \"%s\""), filename);
 670       return NULL;
 671     }
 672
 673   const std::string dirname = ldirname (filename);
 674   auto fetch_another = [&dirname] (const char *name)
 675     {
 676       return xml_fetch_content_from_file (name, dirname.c_str ());
 677     };
 678
 679   return tdesc_parse_xml (tdesc_str->data (), fetch_another);
 680 }
 681
 682 /* Read a string representation of available features from the target,
 683    using TARGET_OBJECT_AVAILABLE_FEATURES.  The returned string is
 684    malloc allocated and NUL-terminated.  NAME should be a non-NULL
 685    string identifying the XML document we want; the top level document
 686    is "target.xml".  Other calls may be performed for the DTD or
 687    for <xi:include>.  */
 688
 689 static std::optional<gdb::char_vector>
 690 fetch_available_features_from_target (const char *name, target_ops *ops)
 691 {
 692   /* Read this object as a string.  This ensures that a NUL
 693      terminator is added.  */
 694   return target_read_stralloc (ops,
 695                                TARGET_OBJECT_AVAILABLE_FEATURES,
 696                                name);
 697 }
 698 \f
 699
 700 /* Read an XML target description using OPS.  Parse it, and return the
 701    parsed description.  */
 702
 703 const struct target_desc *
 704 target_read_description_xml (struct target_ops *ops)
 705 {
 706   std::optional<gdb::char_vector> tdesc_str
 707     = fetch_available_features_from_target ("target.xml", ops);
 708   if (!tdesc_str)
 709     return NULL;
 710
 711   auto fetch_another = [ops] (const char *name)
 712     {
 713       return fetch_available_features_from_target (name, ops);
 714     };
 715
 716   return tdesc_parse_xml (tdesc_str->data (), fetch_another);
 717 }
 718
 719 /* Fetches an XML target description using OPS,  processing
 720    includes, but not parsing it.  Used to dump whole tdesc
 721    as a single XML file.  */
 722
 723 std::optional<std::string>
 724 target_fetch_description_xml (struct target_ops *ops)
 725 {
 726 #if !defined(HAVE_LIBEXPAT)
 727   static int have_warned;
 728
 729   if (!have_warned)
 730     {
 731       have_warned = 1;
 732       warning (_("Can not fetch XML target description; XML support was "
 733                  "disabled at compile time"));
 734     }
 735
 736   return {};
 737 #else
 738   std::optional<gdb::char_vector>
 739     tdesc_str = fetch_available_features_from_target ("target.xml", ops);
 740   if (!tdesc_str)
 741     return {};
 742
 743   auto fetch_another = [ops] (const char *name)
 744     {
 745       return fetch_available_features_from_target (name, ops);
 746     };
 747   std::string output;
 748   if (!xml_process_xincludes (output,
 749                               _("target description"),
 750                               tdesc_str->data (), fetch_another, 0))
 751     {
 752       warning (_("Could not load XML target description; ignoring"));
 753       return {};
 754     }
 755   return output;
 756 #endif
 757 }
 758
 759 /* See xml-tdesc.h.  */
 760
 761 const struct target_desc *
 762 string_read_description_xml (const char *xml)
 763 {
 764   return tdesc_parse_xml (xml, [] (const char *href)
 765     {
 766       error (_("xincludes are unsupported with this method"));
 767       return std::optional<gdb::char_vector> ();
 768     });
 769 }