gdb/dwarf2/read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef DWARF2READ_H
  21 #define DWARF2READ_H
  22
  23 #include <queue>
  24 #include <unordered_map>
  25 #include "dwarf2/index-cache.h"
  26 #include "dwarf2/section.h"
  27 #include "filename-seen-cache.h"
  28 #include "gdb_obstack.h"
  29 #include "gdbsupport/hash_enum.h"
  30 #include "psympriv.h"
  31
  32 /* Hold 'maintenance (set|show) dwarf' commands.  */
  33 extern struct cmd_list_element *set_dwarf_cmdlist;
  34 extern struct cmd_list_element *show_dwarf_cmdlist;
  35
  36 struct tu_stats
  37 {
  38   int nr_uniq_abbrev_tables;
  39   int nr_symtabs;
  40   int nr_symtab_sharers;
  41   int nr_stmt_less_type_units;
  42   int nr_all_type_units_reallocs;
  43 };
  44
  45 struct dwarf2_debug_sections;
  46 struct dwarf2_per_cu_data;
  47 struct mapped_index;
  48 struct mapped_debug_names;
  49 struct signatured_type;
  50
  51 /* One item on the queue of compilation units to read in full symbols
  52    for.  */
  53 struct dwarf2_queue_item
  54 {
  55   dwarf2_queue_item (dwarf2_per_cu_data *cu, enum language lang)
  56     : per_cu (cu),
  57       pretend_language (lang)
  58   {
  59   }
  60
  61   ~dwarf2_queue_item ();
  62
  63   DISABLE_COPY_AND_ASSIGN (dwarf2_queue_item);
  64
  65   struct dwarf2_per_cu_data *per_cu;
  66   enum language pretend_language;
  67 };
  68
  69 /* Collection of data recorded per objfile.
  70    This hangs off of dwarf2_objfile_data_key.  */
  71
  72 struct dwarf2_per_objfile
  73 {
  74   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
  75      dwarf2 section names, or is NULL if the standard ELF names are
  76      used.  CAN_COPY is true for formats where symbol
  77      interposition is possible and so symbol values must follow copy
  78      relocation rules.  */
  79   dwarf2_per_objfile (struct objfile *objfile,
  80                       const dwarf2_debug_sections *names,
  81                       bool can_copy);
  82
  83   ~dwarf2_per_objfile ();
  84
  85   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
  86
  87   /* Return the CU/TU given its index.
  88
  89      This is intended for loops like:
  90
  91      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
  92                       + dwarf2_per_objfile->n_type_units); ++i)
  93        {
  94          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
  95
  96          ...;
  97        }
  98   */
  99   dwarf2_per_cu_data *get_cutu (int index);
 100
 101   /* Return the CU given its index.
 102      This differs from get_cutu in that it's for when you know INDEX refers to a
 103      CU.  */
 104   dwarf2_per_cu_data *get_cu (int index);
 105
 106   /* Return the TU given its index.
 107      This differs from get_cutu in that it's for when you know INDEX refers to a
 108      TU.  */
 109   signatured_type *get_tu (int index);
 110
 111   /* Free all cached compilation units.  */
 112   void free_cached_comp_units ();
 113
 114   /* A convenience function to allocate a dwarf2_per_cu_data.  The
 115      returned object has its "index" field set properly.  The object
 116      is allocated on the dwarf2_per_objfile obstack.  */
 117   dwarf2_per_cu_data *allocate_per_cu ();
 118
 119   /* A convenience function to allocate a signatured_type.  The
 120      returned object has its "index" field set properly.  The object
 121      is allocated on the dwarf2_per_objfile obstack.  */
 122   signatured_type *allocate_signatured_type ();
 123
 124   /* Return pointer to string at .debug_line_str offset as read from BUF.
 125      BUF is assumed to be in a compilation unit described by CU_HEADER.
 126      Return *BYTES_READ_PTR count of bytes read from BUF.  */
 127   const char *read_line_string (const gdb_byte *buf,
 128                                 const struct comp_unit_head *cu_header,
 129                                 unsigned int *bytes_read_ptr);
 130
 131 private:
 132   /* This function is mapped across the sections and remembers the
 133      offset and size of each of the debugging sections we are
 134      interested in.  */
 135   void locate_sections (bfd *abfd, asection *sectp,
 136                         const dwarf2_debug_sections &names);
 137
 138 public:
 139   /* Objects that can be shared across objfiles are stored in this
 140      obstack or on the psymtab obstack, while objects that are
 141      objfile-specific are stored on the objfile obstack.  */
 142   auto_obstack obstack;
 143
 144   dwarf2_section_info info {};
 145   dwarf2_section_info abbrev {};
 146   dwarf2_section_info line {};
 147   dwarf2_section_info loc {};
 148   dwarf2_section_info loclists {};
 149   dwarf2_section_info macinfo {};
 150   dwarf2_section_info macro {};
 151   dwarf2_section_info str {};
 152   dwarf2_section_info str_offsets {};
 153   dwarf2_section_info line_str {};
 154   dwarf2_section_info ranges {};
 155   dwarf2_section_info rnglists {};
 156   dwarf2_section_info addr {};
 157   dwarf2_section_info frame {};
 158   dwarf2_section_info eh_frame {};
 159   dwarf2_section_info gdb_index {};
 160   dwarf2_section_info debug_names {};
 161   dwarf2_section_info debug_aranges {};
 162
 163   std::vector<dwarf2_section_info> types;
 164
 165   /* Back link.  */
 166   struct objfile *objfile = NULL;
 167
 168   /* Table of all the compilation units.  This is used to locate
 169      the target compilation unit of a particular reference.  */
 170   std::vector<dwarf2_per_cu_data *> all_comp_units;
 171
 172   /* The .debug_types-related CUs (TUs).  */
 173   std::vector<signatured_type *> all_type_units;
 174
 175   /* Table of struct type_unit_group objects.
 176      The hash key is the DW_AT_stmt_list value.  */
 177   htab_up type_unit_groups;
 178
 179   /* A table mapping .debug_types signatures to its signatured_type entry.
 180      This is NULL if the .debug_types section hasn't been read in yet.  */
 181   htab_up signatured_types;
 182
 183   /* Type unit statistics, to see how well the scaling improvements
 184      are doing.  */
 185   struct tu_stats tu_stats {};
 186
 187   /* A chain of compilation units that are currently read in, so that
 188      they can be freed later.  */
 189   dwarf2_per_cu_data *read_in_chain = NULL;
 190
 191   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 192      This is NULL if the table hasn't been allocated yet.  */
 193   htab_up dwo_files;
 194
 195   /* True if we've checked for whether there is a DWP file.  */
 196   bool dwp_checked = false;
 197
 198   /* The DWP file if there is one, or NULL.  */
 199   std::unique_ptr<struct dwp_file> dwp_file;
 200
 201   /* The shared '.dwz' file, if one exists.  This is used when the
 202      original data was compressed using 'dwz -m'.  */
 203   std::unique_ptr<struct dwz_file> dwz_file;
 204
 205   /* Whether copy relocations are supported by this object format.  */
 206   bool can_copy;
 207
 208   /* A flag indicating whether this objfile has a section loaded at a
 209      VMA of 0.  */
 210   bool has_section_at_zero = false;
 211
 212   /* True if we are using the mapped index,
 213      or we are faking it for OBJF_READNOW's sake.  */
 214   bool using_index = false;
 215
 216   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 217   std::unique_ptr<mapped_index> index_table;
 218
 219   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 220   std::unique_ptr<mapped_debug_names> debug_names_table;
 221
 222   /* When using index_table, this keeps track of all quick_file_names entries.
 223      TUs typically share line table entries with a CU, so we maintain a
 224      separate table of all line table entries to support the sharing.
 225      Note that while there can be way more TUs than CUs, we've already
 226      sorted all the TUs into "type unit groups", grouped by their
 227      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 228      CU and its associated TU group if there is one.  */
 229   htab_up quick_file_names_table;
 230
 231   /* Set during partial symbol reading, to prevent queueing of full
 232      symbols.  */
 233   bool reading_partial_symbols = false;
 234
 235   /* Table mapping type DIEs to their struct type *.
 236      This is NULL if not allocated yet.
 237      The mapping is done via (CU/TU + DIE offset) -> type.  */
 238   htab_up die_type_hash;
 239
 240   /* The CUs we recently read.  */
 241   std::vector<dwarf2_per_cu_data *> just_read_cus;
 242
 243   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 244   htab_up line_header_hash;
 245
 246   /* Table containing all filenames.  This is an optional because the
 247      table is lazily constructed on first access.  */
 248   gdb::optional<filename_seen_cache> filenames_cache;
 249
 250   /* If we loaded the index from an external file, this contains the
 251      resources associated to the open file, memory mapping, etc.  */
 252   std::unique_ptr<index_cache_resource> index_cache_res;
 253
 254   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 255      DW_AT_abstract_origin.  */
 256   std::unordered_map<sect_offset, std::vector<sect_offset>,
 257                      gdb::hash_enum<sect_offset>>
 258     abstract_to_concrete;
 259
 260   /* CUs that are queued to be read.  */
 261   std::queue<dwarf2_queue_item> queue;
 262
 263 private:
 264
 265   /* The total number of per_cu and signatured_type objects that have
 266      been created so far for this reader.  */
 267   size_t m_num_psymtabs = 0;
 268 };
 269
 270 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 271
 272 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 273
 274 /* A partial symtab specialized for DWARF.  */
 275 struct dwarf2_psymtab : public standard_psymtab
 276 {
 277   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 278                   dwarf2_per_cu_data *per_cu)
 279     : standard_psymtab (filename, objfile, 0),
 280       per_cu_data (per_cu)
 281   {
 282   }
 283
 284   void read_symtab (struct objfile *) override;
 285   void expand_psymtab (struct objfile *) override;
 286
 287   struct dwarf2_per_cu_data *per_cu_data;
 288 };
 289
 290 /* Persistent data held for a compilation unit, even when not
 291    processing it.  We put a pointer to this structure in the
 292    psymtab.  */
 293
 294 struct dwarf2_per_cu_data
 295 {
 296   /* The start offset and length of this compilation unit.
 297      NOTE: Unlike comp_unit_head.length, this length includes
 298      initial_length_size.
 299      If the DIE refers to a DWO file, this is always of the original die,
 300      not the DWO file.  */
 301   sect_offset sect_off;
 302   unsigned int length;
 303
 304   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 305   short dwarf_version;
 306
 307   /* Flag indicating this compilation unit will be read in before
 308      any of the current compilation units are processed.  */
 309   unsigned int queued : 1;
 310
 311   /* This flag will be set when reading partial DIEs if we need to load
 312      absolutely all DIEs for this compilation unit, instead of just the ones
 313      we think are interesting.  It gets set if we look for a DIE in the
 314      hash table and don't find it.  */
 315   unsigned int load_all_dies : 1;
 316
 317   /* Non-zero if this CU is from .debug_types.
 318      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 319      this is non-zero.  */
 320   unsigned int is_debug_types : 1;
 321
 322   /* Non-zero if this CU is from the .dwz file.  */
 323   unsigned int is_dwz : 1;
 324
 325   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 326      This flag is only valid if is_debug_types is true.
 327      We can't read a CU directly from a DWO file: There are required
 328      attributes in the stub.  */
 329   unsigned int reading_dwo_directly : 1;
 330
 331   /* Non-zero if the TU has been read.
 332      This is used to assist the "Stay in DWO Optimization" for Fission:
 333      When reading a DWO, it's faster to read TUs from the DWO instead of
 334      fetching them from random other DWOs (due to comdat folding).
 335      If the TU has already been read, the optimization is unnecessary
 336      (and unwise - we don't want to change where gdb thinks the TU lives
 337      "midflight").
 338      This flag is only valid if is_debug_types is true.  */
 339   unsigned int tu_read : 1;
 340
 341   /* Our index in the unshared "symtabs" vector.  */
 342   unsigned index;
 343
 344   /* The section this CU/TU lives in.
 345      If the DIE refers to a DWO file, this is always the original die,
 346      not the DWO file.  */
 347   struct dwarf2_section_info *section;
 348
 349   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 350      of the CU cache it gets reset to NULL again.  This is left as NULL for
 351      dummy CUs (a CU header, but nothing else).  */
 352   struct dwarf2_cu *cu;
 353
 354   /* The unit type of this CU.  */
 355   enum dwarf_unit_type unit_type;
 356
 357   /* The language of this CU.  */
 358   enum language lang;
 359
 360   /* The corresponding dwarf2_per_objfile.  */
 361   struct dwarf2_per_objfile *dwarf2_per_objfile;
 362
 363   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 364      is active.  Otherwise, the 'psymtab' field is active.  */
 365   union
 366   {
 367     /* The partial symbol table associated with this compilation unit,
 368        or NULL for unread partial units.  */
 369     dwarf2_psymtab *psymtab;
 370
 371     /* Data needed by the "quick" functions.  */
 372     struct dwarf2_per_cu_quick_data *quick;
 373   } v;
 374
 375   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 376      while reading psymtabs, used to compute the psymtab dependencies,
 377      and then cleared.  Then it is filled in again while reading full
 378      symbols, and only deleted when the objfile is destroyed.
 379
 380      This is also used to work around a difference between the way gold
 381      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 382      is a gold bug.  For symbols coming from TUs, gold records in the index
 383      the CU that includes the TU instead of the TU itself.  This breaks
 384      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 385      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 386      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 387      we need to look in TU Z to find X.  Fortunately, this is akin to
 388      DW_TAG_imported_unit, so we just use the same mechanism: For
 389      .gdb_index version <=7 this also records the TUs that the CU referred
 390      to.  Concurrently with this change gdb was modified to emit version 8
 391      indices so we only pay a price for gold generated indices.
 392      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 393
 394      This currently needs to be a public member due to how
 395      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 396      could be refactored to make this private.  Until then please try to
 397      avoid direct access to this member, and instead use the helper
 398      functions above.  */
 399   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 400
 401   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 402   bool imported_symtabs_empty () const
 403   {
 404     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 405   }
 406
 407   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 408      first if required.  */
 409   void imported_symtabs_push (dwarf2_per_cu_data *p)
 410   {
 411     if (imported_symtabs == nullptr)
 412       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 413     imported_symtabs->push_back (p);
 414   }
 415
 416   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 417      return 0.  */
 418   size_t imported_symtabs_size () const
 419   {
 420     if (imported_symtabs == nullptr)
 421       return 0;
 422     return imported_symtabs->size ();
 423   }
 424
 425   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 426   void imported_symtabs_free ()
 427   {
 428     delete imported_symtabs;
 429     imported_symtabs = nullptr;
 430   }
 431
 432   /* Return the OBJFILE associated with this compilation unit.  If
 433      this compilation unit came from a separate debuginfo file, then
 434      the master objfile is returned.  */
 435   struct objfile *objfile () const;
 436
 437   /* Return the address size given in the compilation unit header for
 438      this CU.  */
 439   int addr_size () const;
 440
 441   /* Return the offset size given in the compilation unit header for
 442      this CU.  */
 443   int offset_size () const;
 444
 445   /* Return the DW_FORM_ref_addr size given in the compilation unit
 446      header for this CU.  */
 447   int ref_addr_size () const;
 448
 449   /* Return the text offset of the CU.  The returned offset comes from
 450      this CU's objfile.  If this objfile came from a separate
 451      debuginfo file, then the offset may be different from the
 452      corresponding offset in the parent objfile.  */
 453   CORE_ADDR text_offset () const;
 454
 455   /* Return a type that is a generic pointer type, the size of which
 456      matches the address size given in the compilation unit header for
 457      this CU.  */
 458   struct type *addr_type () const;
 459
 460   /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
 461      UNSIGNED_P controls if the integer is unsigned or not.  */
 462   struct type *int_type (int size_in_bytes, bool unsigned_p) const;
 463
 464   /* Find an integer type the same size as the address size given in
 465      the compilation unit header for this CU.  UNSIGNED_P controls if
 466      the integer is unsigned or not.  */
 467   struct type *addr_sized_int_type (bool unsigned_p) const;
 468
 469   /* Return DWARF version number of this CU.  */
 470   short version () const
 471   {
 472     return dwarf_version;
 473   }
 474
 475   /* A type unit group has a per_cu object that is recognized by
 476      having no section.  */
 477   bool type_unit_group_p () const
 478   {
 479     return section == nullptr;
 480   }
 481 };
 482
 483 /* Entry in the signatured_types hash table.  */
 484
 485 struct signatured_type
 486 {
 487   /* The "per_cu" object of this type.
 488      This struct is used iff per_cu.is_debug_types.
 489      N.B.: This is the first member so that it's easy to convert pointers
 490      between them.  */
 491   struct dwarf2_per_cu_data per_cu;
 492
 493   /* The type's signature.  */
 494   ULONGEST signature;
 495
 496   /* Offset in the TU of the type's DIE, as read from the TU header.
 497      If this TU is a DWO stub and the definition lives in a DWO file
 498      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 499   cu_offset type_offset_in_tu;
 500
 501   /* Offset in the section of the type's DIE.
 502      If the definition lives in a DWO file, this is the offset in the
 503      .debug_types.dwo section.
 504      The value is zero until the actual value is known.
 505      Zero is otherwise not a valid section offset.  */
 506   sect_offset type_offset_in_section;
 507
 508   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 509      can share them.  This points to the containing symtab.  */
 510   struct type_unit_group *type_unit_group;
 511
 512   /* The type.
 513      The first time we encounter this type we fully read it in and install it
 514      in the symbol tables.  Subsequent times we only need the type.  */
 515   struct type *type;
 516
 517   /* Containing DWO unit.
 518      This field is valid iff per_cu.reading_dwo_directly.  */
 519   struct dwo_unit *dwo_unit;
 520 };
 521
 522 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 523    there is no .gnu_debugaltlink section in the file.  Error if there
 524    is such a section but the file cannot be found.  */
 525
 526 extern struct dwz_file *dwarf2_get_dwz_file
 527     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 528
 529 /* Return the type of the DIE at DIE_OFFSET in the CU named by
 530    PER_CU.  */
 531
 532 struct type *dwarf2_get_die_type (cu_offset die_offset,
 533                                   struct dwarf2_per_cu_data *per_cu);
 534
 535 /* Given an index in .debug_addr, fetch the value.
 536    NOTE: This can be called during dwarf expression evaluation,
 537    long after the debug information has been read, and thus per_cu->cu
 538    may no longer exist.  */
 539
 540 CORE_ADDR dwarf2_read_addr_index (dwarf2_per_cu_data *per_cu,
 541                                   unsigned int addr_index);
 542
 543 /* Return DWARF block referenced by DW_AT_location of DIE at SECT_OFF at PER_CU.
 544    Returned value is intended for DW_OP_call*.  Returned
 545    dwarf2_locexpr_baton->data has lifetime of
 546    PER_CU->DWARF2_PER_OBJFILE->OBJFILE.  */
 547
 548 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_sect_off
 549   (sect_offset sect_off, dwarf2_per_cu_data *per_cu,
 550    CORE_ADDR (*get_frame_pc) (void *baton),
 551    void *baton, bool resolve_abstract_p = false);
 552
 553 /* Like dwarf2_fetch_die_loc_sect_off, but take a CU
 554    offset.  */
 555
 556 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_cu_off
 557   (cu_offset offset_in_cu, dwarf2_per_cu_data *per_cu,
 558    CORE_ADDR (*get_frame_pc) (void *baton),
 559    void *baton);
 560
 561 /* If the DIE at SECT_OFF in PER_CU has a DW_AT_const_value, return a
 562    pointer to the constant bytes and set LEN to the length of the
 563    data.  If memory is needed, allocate it on OBSTACK.  If the DIE
 564    does not have a DW_AT_const_value, return NULL.  */
 565
 566 extern const gdb_byte *dwarf2_fetch_constant_bytes
 567   (sect_offset sect_off, dwarf2_per_cu_data *per_cu, obstack *obstack,
 568    LONGEST *len);
 569
 570 /* Return the type of the die at SECT_OFF in PER_CU.  Return NULL if no
 571    valid type for this die is found.  */
 572
 573 struct type *dwarf2_fetch_die_type_sect_off
 574   (sect_offset sect_off, dwarf2_per_cu_data *per_cu);
 575
 576 /* When non-zero, dump line number entries as they are read in.  */
 577 extern unsigned int dwarf_line_debug;
 578
 579 #endif /* DWARF2READ_H */