gdb/xml-tdesc.c

   1 /* XML target description support for GDB.
   2
   3    Copyright (C) 2006-2020 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 #include "filenames.h"
  29 #include <unordered_map>
  30 #include <string>
  31
  32 /* Maximum sizes.
  33    This is just to catch obviously wrong values.  */
  34 #define MAX_FIELD_SIZE 65536
  35 #define MAX_FIELD_BITSIZE (MAX_FIELD_SIZE * TARGET_CHAR_BIT)
  36 #define MAX_VECTOR_SIZE 65536
  37
  38 #if !defined(HAVE_LIBEXPAT)
  39
  40 /* Parse DOCUMENT into a target description.  Or don't, since we don't have
  41    an XML parser.  */
  42
  43 static struct target_desc *
  44 tdesc_parse_xml (const char *document, xml_fetch_another fetcher,
  45                  void *fetcher_baton)
  46 {
  47   static int have_warned;
  48
  49   if (!have_warned)
  50     {
  51       have_warned = 1;
  52       warning (_("Can not parse XML target description; XML support was "
  53                  "disabled at compile time"));
  54     }
  55
  56   return NULL;
  57 }
  58
  59 #else /* HAVE_LIBEXPAT */
  60
  61 /* A record of every XML description we have parsed.  We never discard
  62    old descriptions, because we never discard gdbarches.  As long as we
  63    have a gdbarch referencing this description, we want to have a copy
  64    of it here, so that if we parse the same XML document again we can
  65    return the same "struct target_desc *"; if they are not singletons,
  66    then we will create unnecessary duplicate gdbarches.  See
  67    gdbarch_list_lookup_by_info.  */
  68
  69 static std::unordered_map<std::string, target_desc_up> xml_cache;
  70
  71 /* Callback data for target description parsing.  */
  72
  73 struct tdesc_parsing_data
  74 {
  75   /* The target description we are building.  */
  76   struct target_desc *tdesc;
  77
  78   /* The target feature we are currently parsing, or last parsed.  */
  79   struct tdesc_feature *current_feature;
  80
  81   /* The register number to use for the next register we see, if
  82      it does not have its own.  This starts at zero.  */
  83   int next_regnum;
  84
  85   /* The struct or union we are currently parsing, or last parsed.  */
  86   tdesc_type_with_fields *current_type;
  87
  88   /* The byte size of the current struct/flags type, if specified.  Zero
  89      if not specified.  Flags values must specify a size.  */
  90   int current_type_size;
  91 };
  92
  93 /* Handle the end of an <architecture> element and its value.  */
  94
  95 static void
  96 tdesc_end_arch (struct gdb_xml_parser *parser,
  97                 const struct gdb_xml_element *element,
  98                 void *user_data, const char *body_text)
  99 {
 100   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 101   const struct bfd_arch_info *arch;
 102
 103   arch = bfd_scan_arch (body_text);
 104   if (arch == NULL)
 105     gdb_xml_error (parser, _("Target description specified unknown "
 106                              "architecture \"%s\""), body_text);
 107   set_tdesc_architecture (data->tdesc, arch);
 108 }
 109
 110 /* Handle the end of an <osabi> element and its value.  */
 111
 112 static void
 113 tdesc_end_osabi (struct gdb_xml_parser *parser,
 114                  const struct gdb_xml_element *element,
 115                  void *user_data, const char *body_text)
 116 {
 117   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 118   enum gdb_osabi osabi;
 119
 120   osabi = osabi_from_tdesc_string (body_text);
 121   if (osabi == GDB_OSABI_UNKNOWN)
 122     warning (_("Target description specified unknown osabi \"%s\""),
 123              body_text);
 124   else
 125     set_tdesc_osabi (data->tdesc, osabi);
 126 }
 127
 128 /* Handle the end of a <compatible> element and its value.  */
 129
 130 static void
 131 tdesc_end_compatible (struct gdb_xml_parser *parser,
 132                       const struct gdb_xml_element *element,
 133                       void *user_data, const char *body_text)
 134 {
 135   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 136   const struct bfd_arch_info *arch;
 137
 138   arch = bfd_scan_arch (body_text);
 139   tdesc_add_compatible (data->tdesc, arch);
 140 }
 141
 142 /* Handle the start of a <target> element.  */
 143
 144 static void
 145 tdesc_start_target (struct gdb_xml_parser *parser,
 146                     const struct gdb_xml_element *element,
 147                     void *user_data, std::vector<gdb_xml_value> &attributes)
 148 {
 149   char *version
 150     = (char *) xml_find_attribute (attributes, "version")->value.get ();
 151
 152   if (strcmp (version, "1.0") != 0)
 153     gdb_xml_error (parser,
 154                    _("Target description has unsupported version \"%s\""),
 155                    version);
 156 }
 157
 158 /* Handle the start of a <feature> element.  */
 159
 160 static void
 161 tdesc_start_feature (struct gdb_xml_parser *parser,
 162                      const struct gdb_xml_element *element,
 163                      void *user_data, std::vector<gdb_xml_value> &attributes)
 164 {
 165   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 166   char *name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 167
 168   data->current_feature = tdesc_create_feature (data->tdesc, name);
 169 }
 170
 171 /* Handle the start of a <reg> element.  Fill in the optional
 172    attributes and attach it to the containing feature.  */
 173
 174 static void
 175 tdesc_start_reg (struct gdb_xml_parser *parser,
 176                  const struct gdb_xml_element *element,
 177                  void *user_data, std::vector<gdb_xml_value> &attributes)
 178 {
 179   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 180   int ix = 0;
 181   char *name, *group;
 182   const char *type;
 183   int bitsize, regnum, save_restore;
 184
 185   int length = attributes.size ();
 186
 187   name = (char *) attributes[ix++].value.get ();
 188   bitsize = * (ULONGEST *) attributes[ix++].value.get ();
 189
 190   if (ix < length && strcmp (attributes[ix].name, "regnum") == 0)
 191     regnum = * (ULONGEST *) attributes[ix++].value.get ();
 192   else
 193     regnum = data->next_regnum;
 194
 195   if (ix < length && strcmp (attributes[ix].name, "type") == 0)
 196     type = (char *) attributes[ix++].value.get ();
 197   else
 198     type = "int";
 199
 200   if (ix < length && strcmp (attributes[ix].name, "group") == 0)
 201     group = (char *) attributes[ix++].value.get ();
 202   else
 203     group = NULL;
 204
 205   if (ix < length && strcmp (attributes[ix].name, "save-restore") == 0)
 206     save_restore = * (ULONGEST *) attributes[ix++].value.get ();
 207   else
 208     save_restore = 1;
 209
 210   if (strcmp (type, "int") != 0
 211       && strcmp (type, "float") != 0
 212       && tdesc_named_type (data->current_feature, type) == NULL)
 213     gdb_xml_error (parser, _("Register \"%s\" has unknown type \"%s\""),
 214                    name, type);
 215
 216   tdesc_create_reg (data->current_feature, name, regnum, save_restore, group,
 217                     bitsize, type);
 218
 219   data->next_regnum = regnum + 1;
 220 }
 221
 222 /* Handle the start of a <union> element.  Initialize the type and
 223    record it with the current feature.  */
 224
 225 static void
 226 tdesc_start_union (struct gdb_xml_parser *parser,
 227                    const struct gdb_xml_element *element,
 228                    void *user_data, std::vector<gdb_xml_value> &attributes)
 229 {
 230   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 231   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 232
 233   data->current_type = tdesc_create_union (data->current_feature, id);
 234   data->current_type_size = 0;
 235 }
 236
 237 /* Handle the start of a <struct> element.  Initialize the type and
 238    record it with the current feature.  */
 239
 240 static void
 241 tdesc_start_struct (struct gdb_xml_parser *parser,
 242                    const struct gdb_xml_element *element,
 243                    void *user_data, std::vector<gdb_xml_value> &attributes)
 244 {
 245   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 246   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 247   struct gdb_xml_value *attr;
 248
 249   tdesc_type_with_fields *type_with_fields
 250     = tdesc_create_struct (data->current_feature, id);
 251   data->current_type = type_with_fields;
 252   data->current_type_size = 0;
 253
 254   attr = xml_find_attribute (attributes, "size");
 255   if (attr != NULL)
 256     {
 257       ULONGEST size = * (ULONGEST *) attr->value.get ();
 258
 259       if (size > MAX_FIELD_SIZE)
 260         {
 261           gdb_xml_error (parser,
 262                          _("Struct size %s is larger than maximum (%d)"),
 263                          pulongest (size), MAX_FIELD_SIZE);
 264         }
 265       tdesc_set_struct_size (type_with_fields, 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, std::vector<gdb_xml_value> &attributes)
 274 {
 275   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 276   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 277   ULONGEST size = * (ULONGEST *)
 278     xml_find_attribute (attributes, "size")->value.get ();
 279
 280   if (size > MAX_FIELD_SIZE)
 281     {
 282       gdb_xml_error (parser,
 283                      _("Flags size %s is larger than maximum (%d)"),
 284                      pulongest (size), MAX_FIELD_SIZE);
 285     }
 286
 287   data->current_type = tdesc_create_flags (data->current_feature, id, size);
 288   data->current_type_size = size;
 289 }
 290
 291 static void
 292 tdesc_start_enum (struct gdb_xml_parser *parser,
 293                   const struct gdb_xml_element *element,
 294                   void *user_data, std::vector<gdb_xml_value> &attributes)
 295 {
 296   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 297   char *id = (char *) xml_find_attribute (attributes, "id")->value.get ();
 298   int size = * (ULONGEST *)
 299     xml_find_attribute (attributes, "size")->value.get ();
 300
 301   if (size > MAX_FIELD_SIZE)
 302     {
 303       gdb_xml_error (parser,
 304                      _("Enum size %s is larger than maximum (%d)"),
 305                      pulongest (size), MAX_FIELD_SIZE);
 306     }
 307
 308   data->current_type = tdesc_create_enum (data->current_feature, id, size);
 309   data->current_type_size = 0;
 310 }
 311
 312 /* Handle the start of a <field> element.  Attach the field to the
 313    current struct, union or flags.  */
 314
 315 static void
 316 tdesc_start_field (struct gdb_xml_parser *parser,
 317                    const struct gdb_xml_element *element,
 318                    void *user_data, std::vector<gdb_xml_value> &attributes)
 319 {
 320   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 321   struct gdb_xml_value *attr;
 322   struct tdesc_type *field_type;
 323   char *field_name, *field_type_id;
 324   int start, end;
 325
 326   field_name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 327
 328   attr = xml_find_attribute (attributes, "type");
 329   if (attr != NULL)
 330     {
 331       field_type_id = (char *) attr->value.get ();
 332       field_type = tdesc_named_type (data->current_feature, field_type_id);
 333     }
 334   else
 335     {
 336       field_type_id = NULL;
 337       field_type = NULL;
 338     }
 339
 340   attr = xml_find_attribute (attributes, "start");
 341   if (attr != NULL)
 342     {
 343       ULONGEST ul_start = * (ULONGEST *) attr->value.get ();
 344
 345       if (ul_start > MAX_FIELD_BITSIZE)
 346         {
 347           gdb_xml_error (parser,
 348                          _("Field start %s is larger than maximum (%d)"),
 349                          pulongest (ul_start), MAX_FIELD_BITSIZE);
 350         }
 351       start = ul_start;
 352     }
 353   else
 354     start = -1;
 355
 356   attr = xml_find_attribute (attributes, "end");
 357   if (attr != NULL)
 358     {
 359       ULONGEST ul_end = * (ULONGEST *) attr->value.get ();
 360
 361       if (ul_end > MAX_FIELD_BITSIZE)
 362         {
 363           gdb_xml_error (parser,
 364                          _("Field end %s is larger than maximum (%d)"),
 365                          pulongest (ul_end), MAX_FIELD_BITSIZE);
 366         }
 367       end = ul_end;
 368     }
 369   else
 370     end = -1;
 371
 372   if (start != -1)
 373     {
 374       tdesc_type_with_fields *t = data->current_type;
 375
 376       /* Older versions of gdb can't handle elided end values.
 377          Stick with that for now, to help ensure backward compatibility.
 378          E.g., If a newer gdbserver is talking to an older gdb.  */
 379       if (end == -1)
 380         gdb_xml_error (parser, _("Missing end value"));
 381
 382       if (data->current_type_size == 0)
 383         gdb_xml_error (parser,
 384                        _("Bitfields must live in explicitly sized types"));
 385
 386       if (field_type_id != NULL
 387           && strcmp (field_type_id, "bool") == 0
 388           && start != end)
 389         {
 390           gdb_xml_error (parser,
 391                          _("Boolean fields must be one bit in size"));
 392         }
 393
 394       if (end >= 64)
 395         gdb_xml_error (parser,
 396                        _("Bitfield \"%s\" goes past "
 397                          "64 bits (unsupported)"),
 398                        field_name);
 399
 400       /* Assume that the bit numbering in XML is "lsb-zero".  Most
 401          architectures other than PowerPC use this ordering.  In the
 402          future, we can add an XML tag to indicate "msb-zero" numbering.  */
 403       if (start > end)
 404         gdb_xml_error (parser, _("Bitfield \"%s\" has start after end"),
 405                        field_name);
 406       if (end >= data->current_type_size * TARGET_CHAR_BIT)
 407         gdb_xml_error (parser, _("Bitfield \"%s\" does not fit in struct"),
 408                        field_name);
 409
 410       if (field_type != NULL)
 411         tdesc_add_typed_bitfield (t, field_name, start, end, field_type);
 412       else if (start == end)
 413         tdesc_add_flag (t, start, field_name);
 414       else
 415         tdesc_add_bitfield (t, field_name, start, end);
 416     }
 417   else if (start == -1 && end != -1)
 418     gdb_xml_error (parser, _("End specified but not start"));
 419   else if (field_type_id != NULL)
 420     {
 421       /* TDESC_TYPE_FLAGS values are explicitly sized, so the following test
 422          catches adding non-bitfield types to flags as well.  */
 423       if (data->current_type_size != 0)
 424         gdb_xml_error (parser,
 425                        _("Explicitly sized type cannot "
 426                          "contain non-bitfield \"%s\""),
 427                        field_name);
 428
 429       if (field_type == NULL)
 430         gdb_xml_error (parser, _("Field \"%s\" references undefined "
 431                                  "type \"%s\""),
 432                        field_name, field_type_id);
 433
 434       tdesc_add_field (data->current_type, field_name, field_type);
 435     }
 436   else
 437     gdb_xml_error (parser, _("Field \"%s\" has neither type nor bit position"),
 438                    field_name);
 439 }
 440
 441 /* Handle the start of an <evalue> element.  Attach the value to the
 442    current enum.  */
 443
 444 static void
 445 tdesc_start_enum_value (struct gdb_xml_parser *parser,
 446                         const struct gdb_xml_element *element,
 447                         void *user_data, std::vector<gdb_xml_value> &attributes)
 448 {
 449   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 450   struct gdb_xml_value *attr;
 451   char *field_name;
 452   ULONGEST ul_value;
 453   int value;
 454
 455   field_name = (char *) xml_find_attribute (attributes, "name")->value.get ();
 456
 457   attr = xml_find_attribute (attributes, "value");
 458   ul_value = * (ULONGEST *) attr->value.get ();
 459   if (ul_value > INT_MAX)
 460     {
 461       gdb_xml_error (parser,
 462                      _("Enum value %s is larger than maximum (%d)"),
 463                      pulongest (ul_value), INT_MAX);
 464     }
 465   value = ul_value;
 466
 467   tdesc_add_enum_value (data->current_type, value, field_name);
 468 }
 469
 470 /* Handle the start of a <vector> element.  Initialize the type and
 471    record it with the current feature.  */
 472
 473 static void
 474 tdesc_start_vector (struct gdb_xml_parser *parser,
 475                     const struct gdb_xml_element *element,
 476                     void *user_data, std::vector<gdb_xml_value> &attributes)
 477 {
 478   struct tdesc_parsing_data *data = (struct tdesc_parsing_data *) user_data;
 479   struct tdesc_type *field_type;
 480   char *id, *field_type_id;
 481   ULONGEST count;
 482
 483   id = (char *) attributes[0].value.get ();
 484   field_type_id = (char *) attributes[1].value.get ();
 485   count = * (ULONGEST *) attributes[2].value.get ();
 486
 487   if (count > MAX_VECTOR_SIZE)
 488     {
 489       gdb_xml_error (parser,
 490                      _("Vector size %s is larger than maximum (%d)"),
 491                      pulongest (count), MAX_VECTOR_SIZE);
 492     }
 493
 494   field_type = tdesc_named_type (data->current_feature, field_type_id);
 495   if (field_type == NULL)
 496     gdb_xml_error (parser, _("Vector \"%s\" references undefined type \"%s\""),
 497                    id, field_type_id);
 498
 499   tdesc_create_vector (data->current_feature, id, field_type, count);
 500 }
 501
 502 /* The elements and attributes of an XML target description.  */
 503
 504 static const struct gdb_xml_attribute field_attributes[] = {
 505   { "name", GDB_XML_AF_NONE, NULL, NULL },
 506   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 507   { "start", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 508   { "end", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 509   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 510 };
 511
 512 static const struct gdb_xml_attribute enum_value_attributes[] = {
 513   { "name", GDB_XML_AF_NONE, NULL, NULL },
 514   { "value", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 515   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 516 };
 517
 518 static const struct gdb_xml_element struct_union_children[] = {
 519   { "field", field_attributes, NULL, GDB_XML_EF_REPEATABLE,
 520     tdesc_start_field, NULL },
 521   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 522 };
 523
 524 static const struct gdb_xml_element enum_children[] = {
 525   { "evalue", enum_value_attributes, NULL, GDB_XML_EF_REPEATABLE,
 526     tdesc_start_enum_value, NULL },
 527   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 528 };
 529
 530 static const struct gdb_xml_attribute reg_attributes[] = {
 531   { "name", GDB_XML_AF_NONE, NULL, NULL },
 532   { "bitsize", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 533   { "regnum", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL },
 534   { "type", GDB_XML_AF_OPTIONAL, NULL, NULL },
 535   { "group", GDB_XML_AF_OPTIONAL, NULL, NULL },
 536   { "save-restore", GDB_XML_AF_OPTIONAL,
 537     gdb_xml_parse_attr_enum, gdb_xml_enums_boolean },
 538   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 539 };
 540
 541 static const struct gdb_xml_attribute struct_union_attributes[] = {
 542   { "id", GDB_XML_AF_NONE, NULL, NULL },
 543   { "size", GDB_XML_AF_OPTIONAL, gdb_xml_parse_attr_ulongest, NULL},
 544   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 545 };
 546
 547 static const struct gdb_xml_attribute flags_attributes[] = {
 548   { "id", GDB_XML_AF_NONE, NULL, NULL },
 549   { "size", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL},
 550   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 551 };
 552
 553 static const struct gdb_xml_attribute enum_attributes[] = {
 554   { "id", GDB_XML_AF_NONE, NULL, NULL },
 555   { "size", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL},
 556   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 557 };
 558
 559 static const struct gdb_xml_attribute vector_attributes[] = {
 560   { "id", GDB_XML_AF_NONE, NULL, NULL },
 561   { "type", GDB_XML_AF_NONE, NULL, NULL },
 562   { "count", GDB_XML_AF_NONE, gdb_xml_parse_attr_ulongest, NULL },
 563   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 564 };
 565
 566 static const struct gdb_xml_attribute feature_attributes[] = {
 567   { "name", GDB_XML_AF_NONE, NULL, NULL },
 568   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 569 };
 570
 571 static const struct gdb_xml_element feature_children[] = {
 572   { "reg", reg_attributes, NULL,
 573     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 574     tdesc_start_reg, NULL },
 575   { "struct", struct_union_attributes, struct_union_children,
 576     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 577     tdesc_start_struct, NULL },
 578   { "union", struct_union_attributes, struct_union_children,
 579     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 580     tdesc_start_union, NULL },
 581   { "flags", flags_attributes, struct_union_children,
 582     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 583     tdesc_start_flags, NULL },
 584   { "enum", enum_attributes, enum_children,
 585     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 586     tdesc_start_enum, NULL },
 587   { "vector", vector_attributes, NULL,
 588     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 589     tdesc_start_vector, NULL },
 590   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 591 };
 592
 593 static const struct gdb_xml_attribute target_attributes[] = {
 594   { "version", GDB_XML_AF_NONE, NULL, NULL },
 595   { NULL, GDB_XML_AF_NONE, NULL, NULL }
 596 };
 597
 598 static const struct gdb_xml_element target_children[] = {
 599   { "architecture", NULL, NULL, GDB_XML_EF_OPTIONAL,
 600     NULL, tdesc_end_arch },
 601   { "osabi", NULL, NULL, GDB_XML_EF_OPTIONAL,
 602     NULL, tdesc_end_osabi },
 603   { "compatible", NULL, NULL, GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 604     NULL, tdesc_end_compatible },
 605   { "feature", feature_attributes, feature_children,
 606     GDB_XML_EF_OPTIONAL | GDB_XML_EF_REPEATABLE,
 607     tdesc_start_feature, NULL },
 608   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 609 };
 610
 611 static const struct gdb_xml_element tdesc_elements[] = {
 612   { "target", target_attributes, target_children, GDB_XML_EF_NONE,
 613     tdesc_start_target, NULL },
 614   { NULL, NULL, NULL, GDB_XML_EF_NONE, NULL, NULL }
 615 };
 616
 617 /* Parse DOCUMENT into a target description and return it.  */
 618
 619 static struct target_desc *
 620 tdesc_parse_xml (const char *document, xml_fetch_another fetcher,
 621                  void *fetcher_baton)
 622 {
 623   struct tdesc_parsing_data data;
 624
 625   /* Expand all XInclude directives.  */
 626   std::string expanded_text;
 627
 628   if (!xml_process_xincludes (expanded_text,
 629                               _("target description"),
 630                               document, fetcher, fetcher_baton, 0))
 631     {
 632       warning (_("Could not load XML target description; ignoring"));
 633       return NULL;
 634     }
 635
 636   /* Check for an exact match in the list of descriptions we have
 637      previously parsed.  */
 638   const auto it = xml_cache.find (expanded_text);
 639   if (it != xml_cache.end ())
 640     return it->second.get ();
 641
 642   memset (&data, 0, sizeof (struct tdesc_parsing_data));
 643   target_desc_up description (allocate_target_description ());
 644   data.tdesc = description.get ();
 645
 646   if (gdb_xml_parse_quick (_("target description"), "gdb-target.dtd",
 647                            tdesc_elements, expanded_text.c_str (), &data) == 0)
 648     {
 649       /* Parsed successfully.  */
 650       xml_cache.emplace (std::move (expanded_text), std::move (description));
 651       return data.tdesc;
 652     }
 653   else
 654     {
 655       warning (_("Could not load XML target description; ignoring"));
 656       return NULL;
 657     }
 658 }
 659 #endif /* HAVE_LIBEXPAT */
 660 \f
 661
 662 /* Read an XML target description from FILENAME.  Parse it, and return
 663    the parsed description.  */
 664
 665 const struct target_desc *
 666 file_read_description_xml (const char *filename)
 667 {
 668   gdb::optional<gdb::char_vector> tdesc_str
 669     = xml_fetch_content_from_file (filename, NULL);
 670   if (!tdesc_str)
 671     {
 672       warning (_("Could not open \"%s\""), filename);
 673       return NULL;
 674     }
 675
 676   return tdesc_parse_xml (tdesc_str->data (), xml_fetch_content_from_file,
 677                           (void *) ldirname (filename).c_str ());
 678 }
 679
 680 /* Read a string representation of available features from the target,
 681    using TARGET_OBJECT_AVAILABLE_FEATURES.  The returned string is
 682    malloc allocated and NUL-terminated.  NAME should be a non-NULL
 683    string identifying the XML document we want; the top level document
 684    is "target.xml".  Other calls may be performed for the DTD or
 685    for <xi:include>.  */
 686
 687 static gdb::optional<gdb::char_vector>
 688 fetch_available_features_from_target (const char *name, void *baton_)
 689 {
 690   struct target_ops *ops = (struct target_ops *) baton_;
 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   gdb::optional<gdb::char_vector> tdesc_str
 707     = fetch_available_features_from_target ("target.xml", ops);
 708   if (!tdesc_str)
 709     return NULL;
 710
 711   return tdesc_parse_xml (tdesc_str->data (),
 712                           fetch_available_features_from_target,
 713                           ops);
 714 }
 715
 716 /* Fetches an XML target description using OPS,  processing
 717    includes, but not parsing it.  Used to dump whole tdesc
 718    as a single XML file.  */
 719
 720 gdb::optional<std::string>
 721 target_fetch_description_xml (struct target_ops *ops)
 722 {
 723 #if !defined(HAVE_LIBEXPAT)
 724   static int have_warned;
 725
 726   if (!have_warned)
 727     {
 728       have_warned = 1;
 729       warning (_("Can not fetch XML target description; XML support was "
 730                  "disabled at compile time"));
 731     }
 732
 733   return {};
 734 #else
 735   gdb::optional<gdb::char_vector>
 736     tdesc_str = fetch_available_features_from_target ("target.xml", ops);
 737   if (!tdesc_str)
 738     return {};
 739
 740   std::string output;
 741   if (!xml_process_xincludes (output,
 742                               _("target description"),
 743                               tdesc_str->data (),
 744                               fetch_available_features_from_target, ops, 0))
 745     {
 746       warning (_("Could not load XML target description; ignoring"));
 747       return {};
 748     }
 749   return output;
 750 #endif
 751 }
 752
 753 /* See xml-tdesc.h.  */
 754
 755 const struct target_desc *
 756 string_read_description_xml (const char *xml)
 757 {
 758   return tdesc_parse_xml (xml, [] (const char *href, void *baton)
 759     {
 760       error (_("xincludes are unsupported with this method"));
 761       return gdb::optional<gdb::char_vector> ();
 762     }, nullptr);
 763 }