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 private:
 114   /* This function is mapped across the sections and remembers the
 115      offset and size of each of the debugging sections we are
 116      interested in.  */
 117   void locate_sections (bfd *abfd, asection *sectp,
 118                         const dwarf2_debug_sections &names);
 119
 120 public:
 121   dwarf2_section_info info {};
 122   dwarf2_section_info abbrev {};
 123   dwarf2_section_info line {};
 124   dwarf2_section_info loc {};
 125   dwarf2_section_info loclists {};
 126   dwarf2_section_info macinfo {};
 127   dwarf2_section_info macro {};
 128   dwarf2_section_info str {};
 129   dwarf2_section_info str_offsets {};
 130   dwarf2_section_info line_str {};
 131   dwarf2_section_info ranges {};
 132   dwarf2_section_info rnglists {};
 133   dwarf2_section_info addr {};
 134   dwarf2_section_info frame {};
 135   dwarf2_section_info eh_frame {};
 136   dwarf2_section_info gdb_index {};
 137   dwarf2_section_info debug_names {};
 138   dwarf2_section_info debug_aranges {};
 139
 140   std::vector<dwarf2_section_info> types;
 141
 142   /* Back link.  */
 143   struct objfile *objfile = NULL;
 144
 145   /* Table of all the compilation units.  This is used to locate
 146      the target compilation unit of a particular reference.  */
 147   std::vector<dwarf2_per_cu_data *> all_comp_units;
 148
 149   /* The .debug_types-related CUs (TUs).  */
 150   std::vector<signatured_type *> all_type_units;
 151
 152   /* Table of struct type_unit_group objects.
 153      The hash key is the DW_AT_stmt_list value.  */
 154   htab_up type_unit_groups;
 155
 156   /* A table mapping .debug_types signatures to its signatured_type entry.
 157      This is NULL if the .debug_types section hasn't been read in yet.  */
 158   htab_up signatured_types;
 159
 160   /* Type unit statistics, to see how well the scaling improvements
 161      are doing.  */
 162   struct tu_stats tu_stats {};
 163
 164   /* A chain of compilation units that are currently read in, so that
 165      they can be freed later.  */
 166   dwarf2_per_cu_data *read_in_chain = NULL;
 167
 168   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 169      This is NULL if the table hasn't been allocated yet.  */
 170   htab_up dwo_files;
 171
 172   /* True if we've checked for whether there is a DWP file.  */
 173   bool dwp_checked = false;
 174
 175   /* The DWP file if there is one, or NULL.  */
 176   std::unique_ptr<struct dwp_file> dwp_file;
 177
 178   /* The shared '.dwz' file, if one exists.  This is used when the
 179      original data was compressed using 'dwz -m'.  */
 180   std::unique_ptr<struct dwz_file> dwz_file;
 181
 182   /* Whether copy relocations are supported by this object format.  */
 183   bool can_copy;
 184
 185   /* A flag indicating whether this objfile has a section loaded at a
 186      VMA of 0.  */
 187   bool has_section_at_zero = false;
 188
 189   /* True if we are using the mapped index,
 190      or we are faking it for OBJF_READNOW's sake.  */
 191   bool using_index = false;
 192
 193   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 194   std::unique_ptr<mapped_index> index_table;
 195
 196   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 197   std::unique_ptr<mapped_debug_names> debug_names_table;
 198
 199   /* When using index_table, this keeps track of all quick_file_names entries.
 200      TUs typically share line table entries with a CU, so we maintain a
 201      separate table of all line table entries to support the sharing.
 202      Note that while there can be way more TUs than CUs, we've already
 203      sorted all the TUs into "type unit groups", grouped by their
 204      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 205      CU and its associated TU group if there is one.  */
 206   htab_up quick_file_names_table;
 207
 208   /* Set during partial symbol reading, to prevent queueing of full
 209      symbols.  */
 210   bool reading_partial_symbols = false;
 211
 212   /* Table mapping type DIEs to their struct type *.
 213      This is NULL if not allocated yet.
 214      The mapping is done via (CU/TU + DIE offset) -> type.  */
 215   htab_up die_type_hash;
 216
 217   /* The CUs we recently read.  */
 218   std::vector<dwarf2_per_cu_data *> just_read_cus;
 219
 220   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 221   htab_up line_header_hash;
 222
 223   /* Table containing all filenames.  This is an optional because the
 224      table is lazily constructed on first access.  */
 225   gdb::optional<filename_seen_cache> filenames_cache;
 226
 227   /* If we loaded the index from an external file, this contains the
 228      resources associated to the open file, memory mapping, etc.  */
 229   std::unique_ptr<index_cache_resource> index_cache_res;
 230
 231   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 232      DW_AT_abstract_origin.  */
 233   std::unordered_map<sect_offset, std::vector<sect_offset>,
 234                      gdb::hash_enum<sect_offset>>
 235     abstract_to_concrete;
 236
 237   /* CUs that are queued to be read.  */
 238   std::queue<dwarf2_queue_item> queue;
 239 };
 240
 241 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 242
 243 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 244
 245 /* A partial symtab specialized for DWARF.  */
 246 struct dwarf2_psymtab : public standard_psymtab
 247 {
 248   dwarf2_psymtab (const char *filename, struct objfile *objfile)
 249     : standard_psymtab (filename, objfile)
 250   {
 251   }
 252
 253   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 254                   CORE_ADDR addr)
 255     : standard_psymtab (filename, objfile, addr)
 256   {
 257   }
 258
 259   void read_symtab (struct objfile *) override;
 260   void expand_psymtab (struct objfile *) override;
 261
 262   struct dwarf2_per_cu_data *per_cu_data;
 263 };
 264
 265 /* Persistent data held for a compilation unit, even when not
 266    processing it.  We put a pointer to this structure in the
 267    psymtab.  */
 268
 269 struct dwarf2_per_cu_data
 270 {
 271   /* The start offset and length of this compilation unit.
 272      NOTE: Unlike comp_unit_head.length, this length includes
 273      initial_length_size.
 274      If the DIE refers to a DWO file, this is always of the original die,
 275      not the DWO file.  */
 276   sect_offset sect_off;
 277   unsigned int length;
 278
 279   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 280   short dwarf_version;
 281
 282   /* Flag indicating this compilation unit will be read in before
 283      any of the current compilation units are processed.  */
 284   unsigned int queued : 1;
 285
 286   /* This flag will be set when reading partial DIEs if we need to load
 287      absolutely all DIEs for this compilation unit, instead of just the ones
 288      we think are interesting.  It gets set if we look for a DIE in the
 289      hash table and don't find it.  */
 290   unsigned int load_all_dies : 1;
 291
 292   /* Non-zero if this CU is from .debug_types.
 293      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 294      this is non-zero.  */
 295   unsigned int is_debug_types : 1;
 296
 297   /* Non-zero if this CU is from the .dwz file.  */
 298   unsigned int is_dwz : 1;
 299
 300   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 301      This flag is only valid if is_debug_types is true.
 302      We can't read a CU directly from a DWO file: There are required
 303      attributes in the stub.  */
 304   unsigned int reading_dwo_directly : 1;
 305
 306   /* Non-zero if the TU has been read.
 307      This is used to assist the "Stay in DWO Optimization" for Fission:
 308      When reading a DWO, it's faster to read TUs from the DWO instead of
 309      fetching them from random other DWOs (due to comdat folding).
 310      If the TU has already been read, the optimization is unnecessary
 311      (and unwise - we don't want to change where gdb thinks the TU lives
 312      "midflight").
 313      This flag is only valid if is_debug_types is true.  */
 314   unsigned int tu_read : 1;
 315
 316   /* The section this CU/TU lives in.
 317      If the DIE refers to a DWO file, this is always the original die,
 318      not the DWO file.  */
 319   struct dwarf2_section_info *section;
 320
 321   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 322      of the CU cache it gets reset to NULL again.  This is left as NULL for
 323      dummy CUs (a CU header, but nothing else).  */
 324   struct dwarf2_cu *cu;
 325
 326   /* The corresponding dwarf2_per_objfile.  */
 327   struct dwarf2_per_objfile *dwarf2_per_objfile;
 328
 329   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 330      is active.  Otherwise, the 'psymtab' field is active.  */
 331   union
 332   {
 333     /* The partial symbol table associated with this compilation unit,
 334        or NULL for unread partial units.  */
 335     dwarf2_psymtab *psymtab;
 336
 337     /* Data needed by the "quick" functions.  */
 338     struct dwarf2_per_cu_quick_data *quick;
 339   } v;
 340
 341   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 342      while reading psymtabs, used to compute the psymtab dependencies,
 343      and then cleared.  Then it is filled in again while reading full
 344      symbols, and only deleted when the objfile is destroyed.
 345
 346      This is also used to work around a difference between the way gold
 347      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 348      is a gold bug.  For symbols coming from TUs, gold records in the index
 349      the CU that includes the TU instead of the TU itself.  This breaks
 350      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 351      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 352      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 353      we need to look in TU Z to find X.  Fortunately, this is akin to
 354      DW_TAG_imported_unit, so we just use the same mechanism: For
 355      .gdb_index version <=7 this also records the TUs that the CU referred
 356      to.  Concurrently with this change gdb was modified to emit version 8
 357      indices so we only pay a price for gold generated indices.
 358      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 359
 360      This currently needs to be a public member due to how
 361      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 362      could be refactored to make this private.  Until then please try to
 363      avoid direct access to this member, and instead use the helper
 364      functions above.  */
 365   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 366
 367   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 368   bool imported_symtabs_empty () const
 369   {
 370     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 371   }
 372
 373   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 374      first if required.  */
 375   void imported_symtabs_push (dwarf2_per_cu_data *p)
 376   {
 377     if (imported_symtabs == nullptr)
 378       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 379     imported_symtabs->push_back (p);
 380   }
 381
 382   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 383      return 0.  */
 384   size_t imported_symtabs_size () const
 385   {
 386     if (imported_symtabs == nullptr)
 387       return 0;
 388     return imported_symtabs->size ();
 389   }
 390
 391   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 392   void imported_symtabs_free ()
 393   {
 394     delete imported_symtabs;
 395     imported_symtabs = nullptr;
 396   }
 397
 398   /* Return the OBJFILE associated with this compilation unit.  If
 399      this compilation unit came from a separate debuginfo file, then
 400      the master objfile is returned.  */
 401   struct objfile *objfile () const;
 402
 403   /* Return the address size given in the compilation unit header for
 404      this CU.  */
 405   int addr_size () const;
 406
 407   /* Return the offset size given in the compilation unit header for
 408      this CU.  */
 409   int offset_size () const;
 410
 411   /* Return the DW_FORM_ref_addr size given in the compilation unit
 412      header for this CU.  */
 413   int ref_addr_size () const;
 414
 415   /* Return the text offset of the CU.  The returned offset comes from
 416      this CU's objfile.  If this objfile came from a separate
 417      debuginfo file, then the offset may be different from the
 418      corresponding offset in the parent objfile.  */
 419   CORE_ADDR text_offset () const;
 420
 421   /* Return a type that is a generic pointer type, the size of which
 422      matches the address size given in the compilation unit header for
 423      this CU.  */
 424   struct type *addr_type () const;
 425
 426   /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
 427      UNSIGNED_P controls if the integer is unsigned or not.  */
 428   struct type *int_type (int size_in_bytes, bool unsigned_p) const;
 429
 430   /* Find an integer type the same size as the address size given in
 431      the compilation unit header for this CU.  UNSIGNED_P controls if
 432      the integer is unsigned or not.  */
 433   struct type *addr_sized_int_type (bool unsigned_p) const;
 434
 435   /* Return DWARF version number of this CU.  */
 436   short version () const
 437   {
 438     return dwarf_version;
 439   }
 440
 441   /* A type unit group has a per_cu object that is recognized by
 442      having no section.  */
 443   bool type_unit_group_p () const
 444   {
 445     return section == nullptr;
 446   }
 447 };
 448
 449 /* Entry in the signatured_types hash table.  */
 450
 451 struct signatured_type
 452 {
 453   /* The "per_cu" object of this type.
 454      This struct is used iff per_cu.is_debug_types.
 455      N.B.: This is the first member so that it's easy to convert pointers
 456      between them.  */
 457   struct dwarf2_per_cu_data per_cu;
 458
 459   /* The type's signature.  */
 460   ULONGEST signature;
 461
 462   /* Offset in the TU of the type's DIE, as read from the TU header.
 463      If this TU is a DWO stub and the definition lives in a DWO file
 464      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 465   cu_offset type_offset_in_tu;
 466
 467   /* Offset in the section of the type's DIE.
 468      If the definition lives in a DWO file, this is the offset in the
 469      .debug_types.dwo section.
 470      The value is zero until the actual value is known.
 471      Zero is otherwise not a valid section offset.  */
 472   sect_offset type_offset_in_section;
 473
 474   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 475      can share them.  This points to the containing symtab.  */
 476   struct type_unit_group *type_unit_group;
 477
 478   /* The type.
 479      The first time we encounter this type we fully read it in and install it
 480      in the symbol tables.  Subsequent times we only need the type.  */
 481   struct type *type;
 482
 483   /* Containing DWO unit.
 484      This field is valid iff per_cu.reading_dwo_directly.  */
 485   struct dwo_unit *dwo_unit;
 486 };
 487
 488 /* This represents a '.dwz' file.  */
 489
 490 struct dwz_file
 491 {
 492   dwz_file (gdb_bfd_ref_ptr &&bfd)
 493     : dwz_bfd (std::move (bfd))
 494   {
 495   }
 496
 497   const char *filename () const
 498   {
 499     return bfd_get_filename (this->dwz_bfd.get ());
 500   }
 501
 502   /* A dwz file can only contain a few sections.  */
 503   struct dwarf2_section_info abbrev {};
 504   struct dwarf2_section_info info {};
 505   struct dwarf2_section_info str {};
 506   struct dwarf2_section_info line {};
 507   struct dwarf2_section_info macro {};
 508   struct dwarf2_section_info gdb_index {};
 509   struct dwarf2_section_info debug_names {};
 510
 511   /* The dwz's BFD.  */
 512   gdb_bfd_ref_ptr dwz_bfd;
 513
 514   /* If we loaded the index from an external file, this contains the
 515      resources associated to the open file, memory mapping, etc.  */
 516   std::unique_ptr<index_cache_resource> index_cache_res;
 517 };
 518
 519 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 520    there is no .gnu_debugaltlink section in the file.  Error if there
 521    is such a section but the file cannot be found.  */
 522
 523 extern struct dwz_file *dwarf2_get_dwz_file
 524     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 525
 526 /* When non-zero, dump line number entries as they are read in.  */
 527 extern unsigned int dwarf_line_debug;
 528
 529 #endif /* DWARF2READ_H */