gdb/dwarf2read.h

   1 /* DWARF 2 debugging format support for GDB.
   2
   3    Copyright (C) 1994-2019 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 "filename-seen-cache.h"
  26 #include "gdb_obstack.h"
  27 #include "gdbsupport/hash_enum.h"
  28
  29 /* Hold 'maintenance (set|show) dwarf' commands.  */
  30 extern struct cmd_list_element *set_dwarf_cmdlist;
  31 extern struct cmd_list_element *show_dwarf_cmdlist;
  32
  33 typedef struct dwarf2_per_cu_data *dwarf2_per_cu_ptr;
  34 DEF_VEC_P (dwarf2_per_cu_ptr);
  35
  36 extern bool dwarf_always_disassemble;
  37
  38 /* A descriptor for dwarf sections.
  39
  40    S.ASECTION, SIZE are typically initialized when the objfile is first
  41    scanned.  BUFFER, READIN are filled in later when the section is read.
  42    If the section contained compressed data then SIZE is updated to record
  43    the uncompressed size of the section.
  44
  45    DWP file format V2 introduces a wrinkle that is easiest to handle by
  46    creating the concept of virtual sections contained within a real section.
  47    In DWP V2 the sections of the input DWO files are concatenated together
  48    into one section, but section offsets are kept relative to the original
  49    input section.
  50    If this is a virtual dwp-v2 section, S.CONTAINING_SECTION is a backlink to
  51    the real section this "virtual" section is contained in, and BUFFER,SIZE
  52    describe the virtual section.  */
  53
  54 struct dwarf2_section_info
  55 {
  56   union
  57   {
  58     /* If this is a real section, the bfd section.  */
  59     asection *section;
  60     /* If this is a virtual section, pointer to the containing ("real")
  61        section.  */
  62     struct dwarf2_section_info *containing_section;
  63   } s;
  64   /* Pointer to section data, only valid if readin.  */
  65   const gdb_byte *buffer;
  66   /* The size of the section, real or virtual.  */
  67   bfd_size_type size;
  68   /* If this is a virtual section, the offset in the real section.
  69      Only valid if is_virtual.  */
  70   bfd_size_type virtual_offset;
  71   /* True if we have tried to read this section.  */
  72   bool readin;
  73   /* True if this is a virtual section, False otherwise.
  74      This specifies which of s.section and s.containing_section to use.  */
  75   bool is_virtual;
  76 };
  77
  78 /* Read the contents of the section INFO.
  79    OBJFILE is the main object file, but not necessarily the file where
  80    the section comes from.  E.g., for DWO files the bfd of INFO is the bfd
  81    of the DWO file.
  82    If the section is compressed, uncompress it before returning.  */
  83
  84 void dwarf2_read_section (struct objfile *objfile, dwarf2_section_info *info);
  85
  86 struct tu_stats
  87 {
  88   int nr_uniq_abbrev_tables;
  89   int nr_symtabs;
  90   int nr_symtab_sharers;
  91   int nr_stmt_less_type_units;
  92   int nr_all_type_units_reallocs;
  93 };
  94
  95 struct dwarf2_debug_sections;
  96 struct mapped_index;
  97 struct mapped_debug_names;
  98 struct signatured_type;
  99 struct die_info;
 100 typedef struct die_info *die_info_ptr;
 101
 102 /* Collection of data recorded per objfile.
 103    This hangs off of dwarf2_objfile_data_key.  */
 104
 105 struct dwarf2_per_objfile
 106 {
 107   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
 108      dwarf2 section names, or is NULL if the standard ELF names are
 109      used.  CAN_COPY is true for formats where symbol
 110      interposition is possible and so symbol values must follow copy
 111      relocation rules.  */
 112   dwarf2_per_objfile (struct objfile *objfile,
 113                       const dwarf2_debug_sections *names,
 114                       bool can_copy);
 115
 116   ~dwarf2_per_objfile ();
 117
 118   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
 119
 120   /* Return the CU/TU given its index.
 121
 122      This is intended for loops like:
 123
 124      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
 125                       + dwarf2_per_objfile->n_type_units); ++i)
 126        {
 127          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
 128
 129          ...;
 130        }
 131   */
 132   dwarf2_per_cu_data *get_cutu (int index);
 133
 134   /* Return the CU given its index.
 135      This differs from get_cutu in that it's for when you know INDEX refers to a
 136      CU.  */
 137   dwarf2_per_cu_data *get_cu (int index);
 138
 139   /* Return the TU given its index.
 140      This differs from get_cutu in that it's for when you know INDEX refers to a
 141      TU.  */
 142   signatured_type *get_tu (int index);
 143
 144   /* Free all cached compilation units.  */
 145   void free_cached_comp_units ();
 146 private:
 147   /* This function is mapped across the sections and remembers the
 148      offset and size of each of the debugging sections we are
 149      interested in.  */
 150   void locate_sections (bfd *abfd, asection *sectp,
 151                         const dwarf2_debug_sections &names);
 152
 153 public:
 154   dwarf2_section_info info {};
 155   dwarf2_section_info abbrev {};
 156   dwarf2_section_info line {};
 157   dwarf2_section_info loc {};
 158   dwarf2_section_info loclists {};
 159   dwarf2_section_info macinfo {};
 160   dwarf2_section_info macro {};
 161   dwarf2_section_info str {};
 162   dwarf2_section_info line_str {};
 163   dwarf2_section_info ranges {};
 164   dwarf2_section_info rnglists {};
 165   dwarf2_section_info addr {};
 166   dwarf2_section_info frame {};
 167   dwarf2_section_info eh_frame {};
 168   dwarf2_section_info gdb_index {};
 169   dwarf2_section_info debug_names {};
 170   dwarf2_section_info debug_aranges {};
 171
 172   std::vector<dwarf2_section_info> types;
 173
 174   /* Back link.  */
 175   struct objfile *objfile = NULL;
 176
 177   /* Table of all the compilation units.  This is used to locate
 178      the target compilation unit of a particular reference.  */
 179   std::vector<dwarf2_per_cu_data *> all_comp_units;
 180
 181   /* The .debug_types-related CUs (TUs).  */
 182   std::vector<signatured_type *> all_type_units;
 183
 184   /* Table of struct type_unit_group objects.
 185      The hash key is the DW_AT_stmt_list value.  */
 186   htab_t type_unit_groups {};
 187
 188   /* A table mapping .debug_types signatures to its signatured_type entry.
 189      This is NULL if the .debug_types section hasn't been read in yet.  */
 190   htab_t signatured_types {};
 191
 192   /* Type unit statistics, to see how well the scaling improvements
 193      are doing.  */
 194   struct tu_stats tu_stats {};
 195
 196   /* A chain of compilation units that are currently read in, so that
 197      they can be freed later.  */
 198   dwarf2_per_cu_data *read_in_chain = NULL;
 199
 200   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 201      This is NULL if the table hasn't been allocated yet.  */
 202   htab_up dwo_files;
 203
 204   /* True if we've checked for whether there is a DWP file.  */
 205   bool dwp_checked = false;
 206
 207   /* The DWP file if there is one, or NULL.  */
 208   std::unique_ptr<struct dwp_file> dwp_file;
 209
 210   /* The shared '.dwz' file, if one exists.  This is used when the
 211      original data was compressed using 'dwz -m'.  */
 212   std::unique_ptr<struct dwz_file> dwz_file;
 213
 214   /* Whether copy relocations are supported by this object format.  */
 215   bool can_copy;
 216
 217   /* A flag indicating whether this objfile has a section loaded at a
 218      VMA of 0.  */
 219   bool has_section_at_zero = false;
 220
 221   /* True if we are using the mapped index,
 222      or we are faking it for OBJF_READNOW's sake.  */
 223   bool using_index = false;
 224
 225   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 226   std::unique_ptr<mapped_index> index_table;
 227
 228   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 229   std::unique_ptr<mapped_debug_names> debug_names_table;
 230
 231   /* When using index_table, this keeps track of all quick_file_names entries.
 232      TUs typically share line table entries with a CU, so we maintain a
 233      separate table of all line table entries to support the sharing.
 234      Note that while there can be way more TUs than CUs, we've already
 235      sorted all the TUs into "type unit groups", grouped by their
 236      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 237      CU and its associated TU group if there is one.  */
 238   htab_t quick_file_names_table {};
 239
 240   /* Set during partial symbol reading, to prevent queueing of full
 241      symbols.  */
 242   bool reading_partial_symbols = false;
 243
 244   /* Table mapping type DIEs to their struct type *.
 245      This is NULL if not allocated yet.
 246      The mapping is done via (CU/TU + DIE offset) -> type.  */
 247   htab_t die_type_hash {};
 248
 249   /* The CUs we recently read.  */
 250   std::vector<dwarf2_per_cu_data *> just_read_cus;
 251
 252   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 253   htab_t line_header_hash {};
 254
 255   /* Table containing all filenames.  This is an optional because the
 256      table is lazily constructed on first access.  */
 257   gdb::optional<filename_seen_cache> filenames_cache;
 258
 259   /* If we loaded the index from an external file, this contains the
 260      resources associated to the open file, memory mapping, etc.  */
 261   std::unique_ptr<index_cache_resource> index_cache_res;
 262
 263   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 264      DW_AT_abstract_origin.  */
 265   std::unordered_map<sect_offset, std::vector<sect_offset>, \
 266                      gdb::hash_enum<sect_offset>> \
 267     abstract_to_concrete;
 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 /* Persistent data held for a compilation unit, even when not
 275    processing it.  We put a pointer to this structure in the
 276    read_symtab_private field of the psymtab.  */
 277
 278 struct dwarf2_per_cu_data
 279 {
 280   /* The start offset and length of this compilation unit.
 281      NOTE: Unlike comp_unit_head.length, this length includes
 282      initial_length_size.
 283      If the DIE refers to a DWO file, this is always of the original die,
 284      not the DWO file.  */
 285   sect_offset sect_off;
 286   unsigned int length;
 287
 288   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 289   short dwarf_version;
 290
 291   /* Flag indicating this compilation unit will be read in before
 292      any of the current compilation units are processed.  */
 293   unsigned int queued : 1;
 294
 295   /* This flag will be set when reading partial DIEs if we need to load
 296      absolutely all DIEs for this compilation unit, instead of just the ones
 297      we think are interesting.  It gets set if we look for a DIE in the
 298      hash table and don't find it.  */
 299   unsigned int load_all_dies : 1;
 300
 301   /* Non-zero if this CU is from .debug_types.
 302      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 303      this is non-zero.  */
 304   unsigned int is_debug_types : 1;
 305
 306   /* Non-zero if this CU is from the .dwz file.  */
 307   unsigned int is_dwz : 1;
 308
 309   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 310      This flag is only valid if is_debug_types is true.
 311      We can't read a CU directly from a DWO file: There are required
 312      attributes in the stub.  */
 313   unsigned int reading_dwo_directly : 1;
 314
 315   /* Non-zero if the TU has been read.
 316      This is used to assist the "Stay in DWO Optimization" for Fission:
 317      When reading a DWO, it's faster to read TUs from the DWO instead of
 318      fetching them from random other DWOs (due to comdat folding).
 319      If the TU has already been read, the optimization is unnecessary
 320      (and unwise - we don't want to change where gdb thinks the TU lives
 321      "midflight").
 322      This flag is only valid if is_debug_types is true.  */
 323   unsigned int tu_read : 1;
 324
 325   /* The section this CU/TU lives in.
 326      If the DIE refers to a DWO file, this is always the original die,
 327      not the DWO file.  */
 328   struct dwarf2_section_info *section;
 329
 330   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 331      of the CU cache it gets reset to NULL again.  This is left as NULL for
 332      dummy CUs (a CU header, but nothing else).  */
 333   struct dwarf2_cu *cu;
 334
 335   /* The corresponding dwarf2_per_objfile.  */
 336   struct dwarf2_per_objfile *dwarf2_per_objfile;
 337
 338   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 339      is active.  Otherwise, the 'psymtab' field is active.  */
 340   union
 341   {
 342     /* The partial symbol table associated with this compilation unit,
 343        or NULL for unread partial units.  */
 344     struct partial_symtab *psymtab;
 345
 346     /* Data needed by the "quick" functions.  */
 347     struct dwarf2_per_cu_quick_data *quick;
 348   } v;
 349
 350   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 351      while reading psymtabs, used to compute the psymtab dependencies,
 352      and then cleared.  Then it is filled in again while reading full
 353      symbols, and only deleted when the objfile is destroyed.
 354
 355      This is also used to work around a difference between the way gold
 356      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 357      is a gold bug.  For symbols coming from TUs, gold records in the index
 358      the CU that includes the TU instead of the TU itself.  This breaks
 359      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 360      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 361      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 362      we need to look in TU Z to find X.  Fortunately, this is akin to
 363      DW_TAG_imported_unit, so we just use the same mechanism: For
 364      .gdb_index version <=7 this also records the TUs that the CU referred
 365      to.  Concurrently with this change gdb was modified to emit version 8
 366      indices so we only pay a price for gold generated indices.
 367      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.  */
 368   VEC (dwarf2_per_cu_ptr) *imported_symtabs;
 369 };
 370
 371 /* Entry in the signatured_types hash table.  */
 372
 373 struct signatured_type
 374 {
 375   /* The "per_cu" object of this type.
 376      This struct is used iff per_cu.is_debug_types.
 377      N.B.: This is the first member so that it's easy to convert pointers
 378      between them.  */
 379   struct dwarf2_per_cu_data per_cu;
 380
 381   /* The type's signature.  */
 382   ULONGEST signature;
 383
 384   /* Offset in the TU of the type's DIE, as read from the TU header.
 385      If this TU is a DWO stub and the definition lives in a DWO file
 386      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 387   cu_offset type_offset_in_tu;
 388
 389   /* Offset in the section of the type's DIE.
 390      If the definition lives in a DWO file, this is the offset in the
 391      .debug_types.dwo section.
 392      The value is zero until the actual value is known.
 393      Zero is otherwise not a valid section offset.  */
 394   sect_offset type_offset_in_section;
 395
 396   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 397      can share them.  This points to the containing symtab.  */
 398   struct type_unit_group *type_unit_group;
 399
 400   /* The type.
 401      The first time we encounter this type we fully read it in and install it
 402      in the symbol tables.  Subsequent times we only need the type.  */
 403   struct type *type;
 404
 405   /* Containing DWO unit.
 406      This field is valid iff per_cu.reading_dwo_directly.  */
 407   struct dwo_unit *dwo_unit;
 408 };
 409
 410 ULONGEST read_unsigned_leb128 (bfd *, const gdb_byte *, unsigned int *);
 411
 412 /* This represents a '.dwz' file.  */
 413
 414 struct dwz_file
 415 {
 416   dwz_file (gdb_bfd_ref_ptr &&bfd)
 417     : dwz_bfd (std::move (bfd))
 418   {
 419   }
 420
 421   const char *filename () const
 422   {
 423     return bfd_get_filename (this->dwz_bfd.get ());
 424   }
 425
 426   /* A dwz file can only contain a few sections.  */
 427   struct dwarf2_section_info abbrev {};
 428   struct dwarf2_section_info info {};
 429   struct dwarf2_section_info str {};
 430   struct dwarf2_section_info line {};
 431   struct dwarf2_section_info macro {};
 432   struct dwarf2_section_info gdb_index {};
 433   struct dwarf2_section_info debug_names {};
 434
 435   /* The dwz's BFD.  */
 436   gdb_bfd_ref_ptr dwz_bfd;
 437
 438   /* If we loaded the index from an external file, this contains the
 439      resources associated to the open file, memory mapping, etc.  */
 440   std::unique_ptr<index_cache_resource> index_cache_res;
 441 };
 442
 443 /* Open the separate '.dwz' debug file, if needed.  Return NULL if
 444    there is no .gnu_debugaltlink section in the file.  Error if there
 445    is such a section but the file cannot be found.  */
 446
 447 extern struct dwz_file *dwarf2_get_dwz_file
 448     (struct dwarf2_per_objfile *dwarf2_per_objfile);
 449
 450 #endif /* DWARF2READ_H */