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