gdb/dwarf2read.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 "dwarf-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 struct die_info;
  51
  52 /* Collection of data recorded per objfile.
  53    This hangs off of dwarf2_objfile_data_key.  */
  54
  55 struct dwarf2_per_objfile
  56 {
  57   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
  58      dwarf2 section names, or is NULL if the standard ELF names are
  59      used.  CAN_COPY is true for formats where symbol
  60      interposition is possible and so symbol values must follow copy
  61      relocation rules.  */
  62   dwarf2_per_objfile (struct objfile *objfile,
  63                       const dwarf2_debug_sections *names,
  64                       bool can_copy);
  65
  66   ~dwarf2_per_objfile ();
  67
  68   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
  69
  70   /* Return the CU/TU given its index.
  71
  72      This is intended for loops like:
  73
  74      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
  75                       + dwarf2_per_objfile->n_type_units); ++i)
  76        {
  77          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
  78
  79          ...;
  80        }
  81   */
  82   dwarf2_per_cu_data *get_cutu (int index);
  83
  84   /* Return the CU given its index.
  85      This differs from get_cutu in that it's for when you know INDEX refers to a
  86      CU.  */
  87   dwarf2_per_cu_data *get_cu (int index);
  88
  89   /* Return the TU given its index.
  90      This differs from get_cutu in that it's for when you know INDEX refers to a
  91      TU.  */
  92   signatured_type *get_tu (int index);
  93
  94   /* Free all cached compilation units.  */
  95   void free_cached_comp_units ();
  96 private:
  97   /* This function is mapped across the sections and remembers the
  98      offset and size of each of the debugging sections we are
  99      interested in.  */
 100   void locate_sections (bfd *abfd, asection *sectp,
 101                         const dwarf2_debug_sections &names);
 102
 103 public:
 104   dwarf2_section_info info {};
 105   dwarf2_section_info abbrev {};
 106   dwarf2_section_info line {};
 107   dwarf2_section_info loc {};
 108   dwarf2_section_info loclists {};
 109   dwarf2_section_info macinfo {};
 110   dwarf2_section_info macro {};
 111   dwarf2_section_info str {};
 112   dwarf2_section_info str_offsets {};
 113   dwarf2_section_info line_str {};
 114   dwarf2_section_info ranges {};
 115   dwarf2_section_info rnglists {};
 116   dwarf2_section_info addr {};
 117   dwarf2_section_info frame {};
 118   dwarf2_section_info eh_frame {};
 119   dwarf2_section_info gdb_index {};
 120   dwarf2_section_info debug_names {};
 121   dwarf2_section_info debug_aranges {};
 122
 123   std::vector<dwarf2_section_info> types;
 124
 125   /* Back link.  */
 126   struct objfile *objfile = NULL;
 127
 128   /* Table of all the compilation units.  This is used to locate
 129      the target compilation unit of a particular reference.  */
 130   std::vector<dwarf2_per_cu_data *> all_comp_units;
 131
 132   /* The .debug_types-related CUs (TUs).  */
 133   std::vector<signatured_type *> all_type_units;
 134
 135   /* Table of struct type_unit_group objects.
 136      The hash key is the DW_AT_stmt_list value.  */
 137   htab_t type_unit_groups {};
 138
 139   /* A table mapping .debug_types signatures to its signatured_type entry.
 140      This is NULL if the .debug_types section hasn't been read in yet.  */
 141   htab_t signatured_types {};
 142
 143   /* Type unit statistics, to see how well the scaling improvements
 144      are doing.  */
 145   struct tu_stats tu_stats {};
 146
 147   /* A chain of compilation units that are currently read in, so that
 148      they can be freed later.  */
 149   dwarf2_per_cu_data *read_in_chain = NULL;
 150
 151   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 152      This is NULL if the table hasn't been allocated yet.  */
 153   htab_up dwo_files;
 154
 155   /* True if we've checked for whether there is a DWP file.  */
 156   bool dwp_checked = false;
 157
 158   /* The DWP file if there is one, or NULL.  */
 159   std::unique_ptr<struct dwp_file> dwp_file;
 160
 161   /* The shared '.dwz' file, if one exists.  This is used when the
 162      original data was compressed using 'dwz -m'.  */
 163   std::unique_ptr<struct dwz_file> dwz_file;
 164
 165   /* Whether copy relocations are supported by this object format.  */
 166   bool can_copy;
 167
 168   /* A flag indicating whether this objfile has a section loaded at a
 169      VMA of 0.  */
 170   bool has_section_at_zero = false;
 171
 172   /* True if we are using the mapped index,
 173      or we are faking it for OBJF_READNOW's sake.  */
 174   bool using_index = false;
 175
 176   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 177   std::unique_ptr<mapped_index> index_table;
 178
 179   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 180   std::unique_ptr<mapped_debug_names> debug_names_table;
 181
 182   /* When using index_table, this keeps track of all quick_file_names entries.
 183      TUs typically share line table entries with a CU, so we maintain a
 184      separate table of all line table entries to support the sharing.
 185      Note that while there can be way more TUs than CUs, we've already
 186      sorted all the TUs into "type unit groups", grouped by their
 187      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 188      CU and its associated TU group if there is one.  */
 189   htab_t quick_file_names_table {};
 190
 191   /* Set during partial symbol reading, to prevent queueing of full
 192      symbols.  */
 193   bool reading_partial_symbols = false;
 194
 195   /* Table mapping type DIEs to their struct type *.
 196      This is NULL if not allocated yet.
 197      The mapping is done via (CU/TU + DIE offset) -> type.  */
 198   htab_t die_type_hash {};
 199
 200   /* The CUs we recently read.  */
 201   std::vector<dwarf2_per_cu_data *> just_read_cus;
 202
 203   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 204   htab_t line_header_hash {};
 205
 206   /* Table containing all filenames.  This is an optional because the
 207      table is lazily constructed on first access.  */
 208   gdb::optional<filename_seen_cache> filenames_cache;
 209
 210   /* If we loaded the index from an external file, this contains the
 211      resources associated to the open file, memory mapping, etc.  */
 212   std::unique_ptr<index_cache_resource> index_cache_res;
 213
 214   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 215      DW_AT_abstract_origin.  */
 216   std::unordered_map<sect_offset, std::vector<sect_offset>,
 217                      gdb::hash_enum<sect_offset>>
 218     abstract_to_concrete;
 219 };
 220
 221 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 222
 223 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 224
 225 /* A partial symtab specialized for DWARF.  */
 226 struct dwarf2_psymtab : public standard_psymtab
 227 {
 228   dwarf2_psymtab (const char *filename, struct objfile *objfile)
 229     : standard_psymtab (filename, objfile)
 230   {
 231   }
 232
 233   dwarf2_psymtab (const char *filename, struct objfile *objfile,
 234                   CORE_ADDR addr)
 235     : standard_psymtab (filename, objfile, addr)
 236   {
 237   }
 238
 239   void read_symtab (struct objfile *) override;
 240   void expand_psymtab (struct objfile *) override;
 241
 242   struct dwarf2_per_cu_data *per_cu_data;
 243 };
 244
 245 /* Persistent data held for a compilation unit, even when not
 246    processing it.  We put a pointer to this structure in the
 247    psymtab.  */
 248
 249 struct dwarf2_per_cu_data
 250 {
 251   /* The start offset and length of this compilation unit.
 252      NOTE: Unlike comp_unit_head.length, this length includes
 253      initial_length_size.
 254      If the DIE refers to a DWO file, this is always of the original die,
 255      not the DWO file.  */
 256   sect_offset sect_off;
 257   unsigned int length;
 258
 259   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 260   short dwarf_version;
 261
 262   /* Flag indicating this compilation unit will be read in before
 263      any of the current compilation units are processed.  */
 264   unsigned int queued : 1;
 265
 266   /* This flag will be set when reading partial DIEs if we need to load
 267      absolutely all DIEs for this compilation unit, instead of just the ones
 268      we think are interesting.  It gets set if we look for a DIE in the
 269      hash table and don't find it.  */
 270   unsigned int load_all_dies : 1;
 271
 272   /* Non-zero if this CU is from .debug_types.
 273      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 274      this is non-zero.  */
 275   unsigned int is_debug_types : 1;
 276
 277   /* Non-zero if this CU is from the .dwz file.  */
 278   unsigned int is_dwz : 1;
 279
 280   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 281      This flag is only valid if is_debug_types is true.
 282      We can't read a CU directly from a DWO file: There are required
 283      attributes in the stub.  */
 284   unsigned int reading_dwo_directly : 1;
 285
 286   /* Non-zero if the TU has been read.
 287      This is used to assist the "Stay in DWO Optimization" for Fission:
 288      When reading a DWO, it's faster to read TUs from the DWO instead of
 289      fetching them from random other DWOs (due to comdat folding).
 290      If the TU has already been read, the optimization is unnecessary
 291      (and unwise - we don't want to change where gdb thinks the TU lives
 292      "midflight").
 293      This flag is only valid if is_debug_types is true.  */
 294   unsigned int tu_read : 1;
 295
 296   /* The section this CU/TU lives in.
 297      If the DIE refers to a DWO file, this is always the original die,
 298      not the DWO file.  */
 299   struct dwarf2_section_info *section;
 300
 301   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 302      of the CU cache it gets reset to NULL again.  This is left as NULL for
 303      dummy CUs (a CU header, but nothing else).  */
 304   struct dwarf2_cu *cu;
 305
 306   /* The corresponding dwarf2_per_objfile.  */
 307   struct dwarf2_per_objfile *dwarf2_per_objfile;
 308
 309   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 310      is active.  Otherwise, the 'psymtab' field is active.  */
 311   union
 312   {
 313     /* The partial symbol table associated with this compilation unit,
 314        or NULL for unread partial units.  */
 315     dwarf2_psymtab *psymtab;
 316
 317     /* Data needed by the "quick" functions.  */
 318     struct dwarf2_per_cu_quick_data *quick;
 319   } v;
 320
 321   /* Return true of IMPORTED_SYMTABS is empty or not yet allocated.  */
 322   bool imported_symtabs_empty () const
 323   {
 324     return (imported_symtabs == nullptr || imported_symtabs->empty ());
 325   }
 326
 327   /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
 328      first if required.  */
 329   void imported_symtabs_push (dwarf2_per_cu_data *p)
 330   {
 331     if (imported_symtabs == nullptr)
 332       imported_symtabs = new std::vector <dwarf2_per_cu_data *>;
 333     imported_symtabs->push_back (p);
 334   }
 335
 336   /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
 337      return 0.  */
 338   size_t imported_symtabs_size () const
 339   {
 340     if (imported_symtabs == nullptr)
 341       return 0;
 342     return imported_symtabs->size ();
 343   }
 344
 345   /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr.  */
 346   void imported_symtabs_free ()
 347   {
 348     delete imported_symtabs;
 349     imported_symtabs = nullptr;
 350   }
 351
 352   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 353      while reading psymtabs, used to compute the psymtab dependencies,
 354      and then cleared.  Then it is filled in again while reading full
 355      symbols, and only deleted when the objfile is destroyed.
 356
 357      This is also used to work around a difference between the way gold
 358      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 359      is a gold bug.  For symbols coming from TUs, gold records in the index
 360      the CU that includes the TU instead of the TU itself.  This breaks
 361      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 362      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 363      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 364      we need to look in TU Z to find X.  Fortunately, this is akin to
 365      DW_TAG_imported_unit, so we just use the same mechanism: For
 366      .gdb_index version <=7 this also records the TUs that the CU referred
 367      to.  Concurrently with this change gdb was modified to emit version 8
 368      indices so we only pay a price for gold generated indices.
 369      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
 370
 371      This currently needs to be a public member due to how
 372      dwarf2_per_cu_data is allocated and used.  Ideally in future things
 373      could be refactored to make this private.  Until then please try to
 374      avoid direct access to this member, and instead use the helper
 375      functions above.  */
 376   std::vector <dwarf2_per_cu_data *> *imported_symtabs;
 377 };
 378
 379 /* Entry in the signatured_types hash table.  */
 380
 381 struct signatured_type
 382 {
 383   /* The "per_cu" object of this type.
 384      This struct is used iff per_cu.is_debug_types.
 385      N.B.: This is the first member so that it's easy to convert pointers
 386      between them.  */
 387   struct dwarf2_per_cu_data per_cu;
 388
 389   /* The type's signature.  */
 390   ULONGEST signature;
 391
 392   /* Offset in the TU of the type's DIE, as read from the TU header.
 393      If this TU is a DWO stub and the definition lives in a DWO file
 394      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 395   cu_offset type_offset_in_tu;
 396
 397   /* Offset in the section of the type's DIE.
 398      If the definition lives in a DWO file, this is the offset in the
 399      .debug_types.dwo section.
 400      The value is zero until the actual value is known.
 401      Zero is otherwise not a valid section offset.  */
 402   sect_offset type_offset_in_section;
 403
 404   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 405      can share them.  This points to the containing symtab.  */
 406   struct type_unit_group *type_unit_group;
 407
 408   /* The type.
 409      The first time we encounter this type we fully read it in and install it
 410      in the symbol tables.  Subsequent times we only need the type.  */
 411   struct type *type;
 412
 413   /* Containing DWO unit.
 414      This field is valid iff per_cu.reading_dwo_directly.  */
 415   struct dwo_unit *dwo_unit;
 416 };
 417
 418 /* This represents a '.dwz' file.  */
 419
 420 struct dwz_file
 421 {
 422   dwz_file (gdb_bfd_ref_ptr &&bfd)
 423     : dwz_bfd (std::move (bfd))
 424   {
 425   }
 426
 427   const char *filename () const
 428   {
 429     return bfd_get_filename (this->dwz_bfd.get ());
 430   }
 431
 432   /* A dwz file can only contain a few sections.  */
 433   struct dwarf2_section_info abbrev {};
 434   struct dwarf2_section_info info {};
 435   struct dwarf2_section_info str {};
 436   struct dwarf2_section_info line {};
 437   struct dwarf2_section_info macro {};
 438   struct dwarf2_section_info gdb_index {};
 439   struct dwarf2_section_info debug_names {};
 440
 441   /* The dwz's BFD.  */
 442   gdb_bfd_ref_ptr dwz_bfd;
 443
 444   /* If we loaded the index from an external file, this contains the
 445      resources associated to the open file, memory mapping, etc.  */
 446   std::unique_ptr<index_cache_resource> index_cache_res;
 447 };
 448
 449 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 450    there is no .gnu_debugaltlink section in the file.  Error if there
 451    is such a section but the file cannot be found.  */
 452
 453 extern struct dwz_file *dwarf2_get_dwz_file
 454     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 455
 456 #endif /* DWARF2READ_H */