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 <unordered_map>
  24 #include "dwarf2/index-cache.h"
  25 #include "dwarf2/section.h"
  26 #include "filename-seen-cache.h"
  27 #include "gdb_obstack.h"
  28 #include "gdbsupport/hash_enum.h"
  29 #include "psympriv.h"
  30
  31 /* Hold 'maintenance (set|show) dwarf' commands.  */
  32 extern struct cmd_list_element *set_dwarf_cmdlist;
  33 extern struct cmd_list_element *show_dwarf_cmdlist;
  34
  35 extern bool dwarf_always_disassemble;
  36
  37 struct tu_stats
  38 {
  39   int nr_uniq_abbrev_tables;
  40   int nr_symtabs;
  41   int nr_symtab_sharers;
  42   int nr_stmt_less_type_units;
  43   int nr_all_type_units_reallocs;
  44 };
  45
  46 struct dwarf2_debug_sections;
  47 struct mapped_index;
  48 struct mapped_debug_names;
  49 struct signatured_type;
  50
  51 /* Collection of data recorded per objfile.
  52    This hangs off of dwarf2_objfile_data_key.  */
  53
  54 struct dwarf2_per_objfile
  55 {
  56   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
  57      dwarf2 section names, or is NULL if the standard ELF names are
  58      used.  CAN_COPY is true for formats where symbol
  59      interposition is possible and so symbol values must follow copy
  60      relocation rules.  */
  61   dwarf2_per_objfile (struct objfile *objfile,
  62                       const dwarf2_debug_sections *names,
  63                       bool can_copy);
  64
  65   ~dwarf2_per_objfile ();
  66
  67   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
  68
  69   /* Return the CU/TU given its index.
  70
  71      This is intended for loops like:
  72
  73      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
  74                       + dwarf2_per_objfile->n_type_units); ++i)
  75        {
  76          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
  77
  78          ...;
  79        }
  80   */
  81   dwarf2_per_cu_data *get_cutu (int index);
  82
  83   /* Return the CU given its index.
  84      This differs from get_cutu in that it's for when you know INDEX refers to a
  85      CU.  */
  86   dwarf2_per_cu_data *get_cu (int index);
  87
  88   /* Return the TU given its index.
  89      This differs from get_cutu in that it's for when you know INDEX refers to a
  90      TU.  */
  91   signatured_type *get_tu (int index);
  92
  93   /* Free all cached compilation units.  */
  94   void free_cached_comp_units ();
  95 private:
  96   /* This function is mapped across the sections and remembers the
  97      offset and size of each of the debugging sections we are
  98      interested in.  */
  99   void locate_sections (bfd *abfd, asection *sectp,
 100                         const dwarf2_debug_sections &names);
 101
 102 public:
 103   dwarf2_section_info info {};
 104   dwarf2_section_info abbrev {};
 105   dwarf2_section_info line {};
 106   dwarf2_section_info loc {};
 107   dwarf2_section_info loclists {};
 108   dwarf2_section_info macinfo {};
 109   dwarf2_section_info macro {};
 110   dwarf2_section_info str {};
 111   dwarf2_section_info str_offsets {};
 112   dwarf2_section_info line_str {};
 113   dwarf2_section_info ranges {};
 114   dwarf2_section_info rnglists {};
 115   dwarf2_section_info addr {};
 116   dwarf2_section_info frame {};
 117   dwarf2_section_info eh_frame {};
 118   dwarf2_section_info gdb_index {};
 119   dwarf2_section_info debug_names {};
 120   dwarf2_section_info debug_aranges {};
 121
 122   std::vector<dwarf2_section_info> types;
 123
 124   /* Back link.  */
 125   struct objfile *objfile = NULL;
 126
 127   /* Table of all the compilation units.  This is used to locate
 128      the target compilation unit of a particular reference.  */
 129   std::vector<dwarf2_per_cu_data *> all_comp_units;
 130
 131   /* The .debug_types-related CUs (TUs).  */
 132   std::vector<signatured_type *> all_type_units;
 133
 134   /* Table of struct type_unit_group objects.
 135      The hash key is the DW_AT_stmt_list value.  */
 136   htab_t type_unit_groups {};
 137
 138   /* A table mapping .debug_types signatures to its signatured_type entry.
 139      This is NULL if the .debug_types section hasn't been read in yet.  */
 140   htab_t signatured_types {};
 141
 142   /* Type unit statistics, to see how well the scaling improvements
 143      are doing.  */
 144   struct tu_stats tu_stats {};
 145
 146   /* A chain of compilation units that are currently read in, so that
 147      they can be freed later.  */
 148   dwarf2_per_cu_data *read_in_chain = NULL;
 149
 150   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 151      This is NULL if the table hasn't been allocated yet.  */
 152   htab_up dwo_files;
 153
 154   /* True if we've checked for whether there is a DWP file.  */
 155   bool dwp_checked = false;
 156
 157   /* The DWP file if there is one, or NULL.  */
 158   std::unique_ptr<struct dwp_file> dwp_file;
 159
 160   /* The shared '.dwz' file, if one exists.  This is used when the
 161      original data was compressed using 'dwz -m'.  */
 162   std::unique_ptr<struct dwz_file> dwz_file;
 163
 164   /* Whether copy relocations are supported by this object format.  */
 165   bool can_copy;
 166
 167   /* A flag indicating whether this objfile has a section loaded at a
 168      VMA of 0.  */
 169   bool has_section_at_zero = false;
 170
 171   /* True if we are using the mapped index,
 172      or we are faking it for OBJF_READNOW's sake.  */
 173   bool using_index = false;
 174
 175   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 176   std::unique_ptr<mapped_index> index_table;
 177
 178   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 179   std::unique_ptr<mapped_debug_names> debug_names_table;
 180
 181   /* When using index_table, this keeps track of all quick_file_names entries.
 182      TUs typically share line table entries with a CU, so we maintain a
 183      separate table of all line table entries to support the sharing.
 184      Note that while there can be way more TUs than CUs, we've already
 185      sorted all the TUs into "type unit groups", grouped by their
 186      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 187      CU and its associated TU group if there is one.  */
 188   htab_t quick_file_names_table {};
 189
 190   /* Set during partial symbol reading, to prevent queueing of full
 191      symbols.  */
 192   bool reading_partial_symbols = false;
 193
 194   /* Table mapping type DIEs to their struct type *.
 195      This is NULL if not allocated yet.
 196      The mapping is done via (CU/TU + DIE offset) -> type.  */
 197   htab_t die_type_hash {};
 198
 199   /* The CUs we recently read.  */
 200   std::vector<dwarf2_per_cu_data *> just_read_cus;
 201
 202   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 203   htab_t line_header_hash {};
 204
 205   /* Table containing all filenames.  This is an optional because the
 206      table is lazily constructed on first access.  */
 207   gdb::optional<filename_seen_cache> filenames_cache;
 208
 209   /* If we loaded the index from an external file, this contains the
 210      resources associated to the open file, memory mapping, etc.  */
 211   std::unique_ptr<index_cache_resource> index_cache_res;
 212
 213   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 214      DW_AT_abstract_origin.  */
 215   std::unordered_map<sect_offset, std::vector<sect_offset>,
 216                      gdb::hash_enum<sect_offset>>
 217     abstract_to_concrete;
 218 };
 219
 220 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 221
 222 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 223
 224 /* A partial symtab specialized for DWARF.  */
 225 struct dwarf2_psymtab : public standard_psymtab
 226 {
 227   dwarf2_psymtab (const char *filename, struct objfile *objfile)
 228     : standard_psymtab (filename, objfile)
 229   {
 230   }
 231
 232   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 233                   CORE_ADDR addr)
 234     : standard_psymtab (filename, objfile, addr)
 235   {
 236   }
 237
 238   void read_symtab (struct objfile *) override;
 239   void expand_psymtab (struct objfile *) override;
 240
 241   struct dwarf2_per_cu_data *per_cu_data;
 242 };
 243
 244 /* Persistent data held for a compilation unit, even when not
 245    processing it.  We put a pointer to this structure in the
 246    psymtab.  */
 247
 248 struct dwarf2_per_cu_data
 249 {
 250   /* The start offset and length of this compilation unit.
 251      NOTE: Unlike comp_unit_head.length, this length includes
 252      initial_length_size.
 253      If the DIE refers to a DWO file, this is always of the original die,
 254      not the DWO file.  */
 255   sect_offset sect_off;
 256   unsigned int length;
 257
 258   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 259   short dwarf_version;
 260
 261   /* Flag indicating this compilation unit will be read in before
 262      any of the current compilation units are processed.  */
 263   unsigned int queued : 1;
 264
 265   /* This flag will be set when reading partial DIEs if we need to load
 266      absolutely all DIEs for this compilation unit, instead of just the ones
 267      we think are interesting.  It gets set if we look for a DIE in the
 268      hash table and don't find it.  */
 269   unsigned int load_all_dies : 1;
 270
 271   /* Non-zero if this CU is from .debug_types.
 272      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 273      this is non-zero.  */
 274   unsigned int is_debug_types : 1;
 275
 276   /* Non-zero if this CU is from the .dwz file.  */
 277   unsigned int is_dwz : 1;
 278
 279   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 280      This flag is only valid if is_debug_types is true.
 281      We can't read a CU directly from a DWO file: There are required
 282      attributes in the stub.  */
 283   unsigned int reading_dwo_directly : 1;
 284
 285   /* Non-zero if the TU has been read.
 286      This is used to assist the "Stay in DWO Optimization" for Fission:
 287      When reading a DWO, it's faster to read TUs from the DWO instead of
 288      fetching them from random other DWOs (due to comdat folding).
 289      If the TU has already been read, the optimization is unnecessary
 290      (and unwise - we don't want to change where gdb thinks the TU lives
 291      "midflight").
 292      This flag is only valid if is_debug_types is true.  */
 293   unsigned int tu_read : 1;
 294
 295   /* The section this CU/TU lives in.
 296      If the DIE refers to a DWO file, this is always the original die,
 297      not the DWO file.  */
 298   struct dwarf2_section_info *section;
 299
 300   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 301      of the CU cache it gets reset to NULL again.  This is left as NULL for
 302      dummy CUs (a CU header, but nothing else).  */
 303   struct dwarf2_cu *cu;
 304
 305   /* The corresponding dwarf2_per_objfile.  */
 306   struct dwarf2_per_objfile *dwarf2_per_objfile;
 307
 308   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 309      is active.  Otherwise, the 'psymtab' field is active.  */
 310   union
 311   {
 312     /* The partial symbol table associated with this compilation unit,
 313        or NULL for unread partial units.  */
 314     dwarf2_psymtab *psymtab;
 315
 316     /* Data needed by the "quick" functions.  */
 317     struct dwarf2_per_cu_quick_data *quick;
 318   } v;
 319
 320   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 321   bool imported_symtabs_empty () const
 322   {
 323     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 324   }
 325
 326   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 327      first if required.  */
 328   void imported_symtabs_push (dwarf2_per_cu_data *p)
 329   {
 330     if (imported_symtabs == nullptr)
 331       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 332     imported_symtabs->push_back (p);
 333   }
 334
 335   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 336      return 0.  */
 337   size_t imported_symtabs_size () const
 338   {
 339     if (imported_symtabs == nullptr)
 340       return 0;
 341     return imported_symtabs->size ();
 342   }
 343
 344   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 345   void imported_symtabs_free ()
 346   {
 347     delete imported_symtabs;
 348     imported_symtabs = nullptr;
 349   }
 350
 351   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 352      while reading psymtabs, used to compute the psymtab dependencies,
 353      and then cleared.  Then it is filled in again while reading full
 354      symbols, and only deleted when the objfile is destroyed.
 355
 356      This is also used to work around a difference between the way gold
 357      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 358      is a gold bug.  For symbols coming from TUs, gold records in the index
 359      the CU that includes the TU instead of the TU itself.  This breaks
 360      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 361      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 362      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 363      we need to look in TU Z to find X.  Fortunately, this is akin to
 364      DW_TAG_imported_unit, so we just use the same mechanism: For
 365      .gdb_index version <=7 this also records the TUs that the CU referred
 366      to.  Concurrently with this change gdb was modified to emit version 8
 367      indices so we only pay a price for gold generated indices.
 368      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 369
 370      This currently needs to be a public member due to how
 371      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 372      could be refactored to make this private.  Until then please try to
 373      avoid direct access to this member, and instead use the helper
 374      functions above.  */
 375   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 376 };
 377
 378 /* Entry in the signatured_types hash table.  */
 379
 380 struct signatured_type
 381 {
 382   /* The "per_cu" object of this type.
 383      This struct is used iff per_cu.is_debug_types.
 384      N.B.: This is the first member so that it's easy to convert pointers
 385      between them.  */
 386   struct dwarf2_per_cu_data per_cu;
 387
 388   /* The type's signature.  */
 389   ULONGEST signature;
 390
 391   /* Offset in the TU of the type's DIE, as read from the TU header.
 392      If this TU is a DWO stub and the definition lives in a DWO file
 393      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 394   cu_offset type_offset_in_tu;
 395
 396   /* Offset in the section of the type's DIE.
 397      If the definition lives in a DWO file, this is the offset in the
 398      .debug_types.dwo section.
 399      The value is zero until the actual value is known.
 400      Zero is otherwise not a valid section offset.  */
 401   sect_offset type_offset_in_section;
 402
 403   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 404      can share them.  This points to the containing symtab.  */
 405   struct type_unit_group *type_unit_group;
 406
 407   /* The type.
 408      The first time we encounter this type we fully read it in and install it
 409      in the symbol tables.  Subsequent times we only need the type.  */
 410   struct type *type;
 411
 412   /* Containing DWO unit.
 413      This field is valid iff per_cu.reading_dwo_directly.  */
 414   struct dwo_unit *dwo_unit;
 415 };
 416
 417 /* This represents a '.dwz' file.  */
 418
 419 struct dwz_file
 420 {
 421   dwz_file (gdb_bfd_ref_ptr &&bfd)
 422     : dwz_bfd (std::move (bfd))
 423   {
 424   }
 425
 426   const char *filename () const
 427   {
 428     return bfd_get_filename (this->dwz_bfd.get ());
 429   }
 430
 431   /* A dwz file can only contain a few sections.  */
 432   struct dwarf2_section_info abbrev {};
 433   struct dwarf2_section_info info {};
 434   struct dwarf2_section_info str {};
 435   struct dwarf2_section_info line {};
 436   struct dwarf2_section_info macro {};
 437   struct dwarf2_section_info gdb_index {};
 438   struct dwarf2_section_info debug_names {};
 439
 440   /* The dwz's BFD.  */
 441   gdb_bfd_ref_ptr dwz_bfd;
 442
 443   /* If we loaded the index from an external file, this contains the
 444      resources associated to the open file, memory mapping, etc.  */
 445   std::unique_ptr<index_cache_resource> index_cache_res;
 446 };
 447
 448 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 449    there is no .gnu_debugaltlink section in the file.  Error if there
 450    is such a section but the file cannot be found.  */
 451
 452 extern struct dwz_file *dwarf2_get_dwz_file
 453     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 454
 455 #endif /* DWARF2READ_H */