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
  25 /* Local non-gdb includes.  */
  26 #include "dwarf-index-cache.h"
  27 #include "filename-seen-cache.h"
  28 #include "gdb_obstack.h"
  29
  30 /* Hold 'maintenance (set|show) dwarf' commands.  */
  31 extern struct cmd_list_element *set_dwarf_cmdlist;
  32 extern struct cmd_list_element *show_dwarf_cmdlist;
  33
  34 typedef struct dwarf2_per_cu_data *dwarf2_per_cu_ptr;
  35 DEF_VEC_P (dwarf2_per_cu_ptr);
  36
  37 /* A descriptor for dwarf sections.
  38
  39    S.ASECTION, SIZE are typically initialized when the objfile is first
  40    scanned.  BUFFER, READIN are filled in later when the section is read.
  41    If the section contained compressed data then SIZE is updated to record
  42    the uncompressed size of the section.
  43
  44    DWP file format V2 introduces a wrinkle that is easiest to handle by
  45    creating the concept of virtual sections contained within a real section.
  46    In DWP V2 the sections of the input DWO files are concatenated together
  47    into one section, but section offsets are kept relative to the original
  48    input section.
  49    If this is a virtual dwp-v2 section, S.CONTAINING_SECTION is a backlink to
  50    the real section this "virtual" section is contained in, and BUFFER,SIZE
  51    describe the virtual section.  */
  52
  53 struct dwarf2_section_info
  54 {
  55   union
  56   {
  57     /* If this is a real section, the bfd section.  */
  58     asection *section;
  59     /* If this is a virtual section, pointer to the containing ("real")
  60        section.  */
  61     struct dwarf2_section_info *containing_section;
  62   } s;
  63   /* Pointer to section data, only valid if readin.  */
  64   const gdb_byte *buffer;
  65   /* The size of the section, real or virtual.  */
  66   bfd_size_type size;
  67   /* If this is a virtual section, the offset in the real section.
  68      Only valid if is_virtual.  */
  69   bfd_size_type virtual_offset;
  70   /* True if we have tried to read this section.  */
  71   char readin;
  72   /* True if this is a virtual section, False otherwise.
  73      This specifies which of s.section and s.containing_section to use.  */
  74   char is_virtual;
  75 };
  76
  77 typedef struct dwarf2_section_info dwarf2_section_info_def;
  78 DEF_VEC_O (dwarf2_section_info_def);
  79
  80 /* Read the contents of the section INFO.
  81    OBJFILE is the main object file, but not necessarily the file where
  82    the section comes from.  E.g., for DWO files the bfd of INFO is the bfd
  83    of the DWO file.
  84    If the section is compressed, uncompress it before returning.  */
  85
  86 void dwarf2_read_section (struct objfile *objfile, dwarf2_section_info *info);
  87
  88 struct tu_stats
  89 {
  90   int nr_uniq_abbrev_tables;
  91   int nr_symtabs;
  92   int nr_symtab_sharers;
  93   int nr_stmt_less_type_units;
  94   int nr_all_type_units_reallocs;
  95 };
  96
  97 struct dwarf2_debug_sections;
  98 struct mapped_index;
  99 struct mapped_debug_names;
 100 struct signatured_type;
 101 struct die_info;
 102 typedef struct die_info *die_info_ptr;
 103
 104 /* Collection of data recorded per objfile.
 105    This hangs off of dwarf2_objfile_data_key.  */
 106
 107 struct dwarf2_per_objfile : public allocate_on_obstack
 108 {
 109   /* Construct a dwarf2_per_objfile for OBJFILE.  NAMES points to the
 110      dwarf2 section names, or is NULL if the standard ELF names are
 111      used.  */
 112   dwarf2_per_objfile (struct objfile *objfile,
 113                       const dwarf2_debug_sections *names);
 114
 115   ~dwarf2_per_objfile ();
 116
 117   DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile);
 118
 119   /* Return the CU/TU given its index.
 120
 121      This is intended for loops like:
 122
 123      for (i = 0; i < (dwarf2_per_objfile->n_comp_units
 124                       + dwarf2_per_objfile->n_type_units); ++i)
 125        {
 126          dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
 127
 128          ...;
 129        }
 130   */
 131   dwarf2_per_cu_data *get_cutu (int index);
 132
 133   /* Return the CU given its index.
 134      This differs from get_cutu in that it's for when you know INDEX refers to a
 135      CU.  */
 136   dwarf2_per_cu_data *get_cu (int index);
 137
 138   /* Return the TU given its index.
 139      This differs from get_cutu in that it's for when you know INDEX refers to a
 140      TU.  */
 141   signatured_type *get_tu (int index);
 142
 143   /* Free all cached compilation units.  */
 144   void free_cached_comp_units ();
 145 private:
 146   /* This function is mapped across the sections and remembers the
 147      offset and size of each of the debugging sections we are
 148      interested in.  */
 149   void locate_sections (bfd *abfd, asection *sectp,
 150                         const dwarf2_debug_sections &names);
 151
 152 public:
 153   dwarf2_section_info info {};
 154   dwarf2_section_info abbrev {};
 155   dwarf2_section_info line {};
 156   dwarf2_section_info loc {};
 157   dwarf2_section_info loclists {};
 158   dwarf2_section_info macinfo {};
 159   dwarf2_section_info macro {};
 160   dwarf2_section_info str {};
 161   dwarf2_section_info line_str {};
 162   dwarf2_section_info ranges {};
 163   dwarf2_section_info rnglists {};
 164   dwarf2_section_info addr {};
 165   dwarf2_section_info frame {};
 166   dwarf2_section_info eh_frame {};
 167   dwarf2_section_info gdb_index {};
 168   dwarf2_section_info debug_names {};
 169   dwarf2_section_info debug_aranges {};
 170
 171   VEC (dwarf2_section_info_def) *types = NULL;
 172
 173   /* Back link.  */
 174   struct objfile *objfile = NULL;
 175
 176   /* Table of all the compilation units.  This is used to locate
 177      the target compilation unit of a particular reference.  */
 178   std::vector<dwarf2_per_cu_data *> all_comp_units;
 179
 180   /* The .debug_types-related CUs (TUs).  */
 181   std::vector<signatured_type *> all_type_units;
 182
 183   /* Table of struct type_unit_group objects.
 184      The hash key is the DW_AT_stmt_list value.  */
 185   htab_t type_unit_groups {};
 186
 187   /* A table mapping .debug_types signatures to its signatured_type entry.
 188      This is NULL if the .debug_types section hasn't been read in yet.  */
 189   htab_t signatured_types {};
 190
 191   /* Type unit statistics, to see how well the scaling improvements
 192      are doing.  */
 193   struct tu_stats tu_stats {};
 194
 195   /* A chain of compilation units that are currently read in, so that
 196      they can be freed later.  */
 197   dwarf2_per_cu_data *read_in_chain = NULL;
 198
 199   /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
 200      This is NULL if the table hasn't been allocated yet.  */
 201   htab_t dwo_files {};
 202
 203   /* True if we've checked for whether there is a DWP file.  */
 204   bool dwp_checked = false;
 205
 206   /* The DWP file if there is one, or NULL.  */
 207   std::unique_ptr<struct dwp_file> dwp_file;
 208
 209   /* The shared '.dwz' file, if one exists.  This is used when the
 210      original data was compressed using 'dwz -m'.  */
 211   std::unique_ptr<struct dwz_file> dwz_file;
 212
 213   /* A flag indicating whether this objfile has a section loaded at a
 214      VMA of 0.  */
 215   bool has_section_at_zero = false;
 216
 217   /* True if we are using the mapped index,
 218      or we are faking it for OBJF_READNOW's sake.  */
 219   bool using_index = false;
 220
 221   /* The mapped index, or NULL if .gdb_index is missing or not being used.  */
 222   std::unique_ptr<mapped_index> index_table;
 223
 224   /* The mapped index, or NULL if .debug_names is missing or not being used.  */
 225   std::unique_ptr<mapped_debug_names> debug_names_table;
 226
 227   /* When using index_table, this keeps track of all quick_file_names entries.
 228      TUs typically share line table entries with a CU, so we maintain a
 229      separate table of all line table entries to support the sharing.
 230      Note that while there can be way more TUs than CUs, we've already
 231      sorted all the TUs into "type unit groups", grouped by their
 232      DW_AT_stmt_list value.  Therefore the only sharing done here is with a
 233      CU and its associated TU group if there is one.  */
 234   htab_t quick_file_names_table {};
 235
 236   /* Set during partial symbol reading, to prevent queueing of full
 237      symbols.  */
 238   bool reading_partial_symbols = false;
 239
 240   /* Table mapping type DIEs to their struct type *.
 241      This is NULL if not allocated yet.
 242      The mapping is done via (CU/TU + DIE offset) -> type.  */
 243   htab_t die_type_hash {};
 244
 245   /* The CUs we recently read.  */
 246   std::vector<dwarf2_per_cu_data *> just_read_cus;
 247
 248   /* Table containing line_header indexed by offset and offset_in_dwz.  */
 249   htab_t line_header_hash {};
 250
 251   /* Table containing all filenames.  This is an optional because the
 252      table is lazily constructed on first access.  */
 253   gdb::optional<filename_seen_cache> filenames_cache;
 254
 255   /* If we loaded the index from an external file, this contains the
 256      resources associated to the open file, memory mapping, etc.  */
 257   std::unique_ptr<index_cache_resource> index_cache_res;
 258
 259   /* Mapping from abstract origin DIE to concrete DIEs that reference it as
 260      DW_AT_abstract_origin.  */
 261   std::unordered_map<die_info_ptr, std::vector<die_info_ptr>>
 262     abstract_to_concrete;
 263 };
 264
 265 /* Get the dwarf2_per_objfile associated to OBJFILE.  */
 266
 267 dwarf2_per_objfile *get_dwarf2_per_objfile (struct objfile *objfile);
 268
 269 /* Persistent data held for a compilation unit, even when not
 270    processing it.  We put a pointer to this structure in the
 271    read_symtab_private field of the psymtab.  */
 272
 273 struct dwarf2_per_cu_data
 274 {
 275   /* The start offset and length of this compilation unit.
 276      NOTE: Unlike comp_unit_head.length, this length includes
 277      initial_length_size.
 278      If the DIE refers to a DWO file, this is always of the original die,
 279      not the DWO file.  */
 280   sect_offset sect_off;
 281   unsigned int length;
 282
 283   /* DWARF standard version this data has been read from (such as 4 or 5).  */
 284   short dwarf_version;
 285
 286   /* Flag indicating this compilation unit will be read in before
 287      any of the current compilation units are processed.  */
 288   unsigned int queued : 1;
 289
 290   /* This flag will be set when reading partial DIEs if we need to load
 291      absolutely all DIEs for this compilation unit, instead of just the ones
 292      we think are interesting.  It gets set if we look for a DIE in the
 293      hash table and don't find it.  */
 294   unsigned int load_all_dies : 1;
 295
 296   /* Non-zero if this CU is from .debug_types.
 297      Struct dwarf2_per_cu_data is contained in struct signatured_type iff
 298      this is non-zero.  */
 299   unsigned int is_debug_types : 1;
 300
 301   /* Non-zero if this CU is from the .dwz file.  */
 302   unsigned int is_dwz : 1;
 303
 304   /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
 305      This flag is only valid if is_debug_types is true.
 306      We can't read a CU directly from a DWO file: There are required
 307      attributes in the stub.  */
 308   unsigned int reading_dwo_directly : 1;
 309
 310   /* Non-zero if the TU has been read.
 311      This is used to assist the "Stay in DWO Optimization" for Fission:
 312      When reading a DWO, it's faster to read TUs from the DWO instead of
 313      fetching them from random other DWOs (due to comdat folding).
 314      If the TU has already been read, the optimization is unnecessary
 315      (and unwise - we don't want to change where gdb thinks the TU lives
 316      "midflight").
 317      This flag is only valid if is_debug_types is true.  */
 318   unsigned int tu_read : 1;
 319
 320   /* The section this CU/TU lives in.
 321      If the DIE refers to a DWO file, this is always the original die,
 322      not the DWO file.  */
 323   struct dwarf2_section_info *section;
 324
 325   /* Set to non-NULL iff this CU is currently loaded.  When it gets freed out
 326      of the CU cache it gets reset to NULL again.  This is left as NULL for
 327      dummy CUs (a CU header, but nothing else).  */
 328   struct dwarf2_cu *cu;
 329
 330   /* The corresponding dwarf2_per_objfile.  */
 331   struct dwarf2_per_objfile *dwarf2_per_objfile;
 332
 333   /* When dwarf2_per_objfile->using_index is true, the 'quick' field
 334      is active.  Otherwise, the 'psymtab' field is active.  */
 335   union
 336   {
 337     /* The partial symbol table associated with this compilation unit,
 338        or NULL for unread partial units.  */
 339     struct partial_symtab *psymtab;
 340
 341     /* Data needed by the "quick" functions.  */
 342     struct dwarf2_per_cu_quick_data *quick;
 343   } v;
 344
 345   /* The CUs we import using DW_TAG_imported_unit.  This is filled in
 346      while reading psymtabs, used to compute the psymtab dependencies,
 347      and then cleared.  Then it is filled in again while reading full
 348      symbols, and only deleted when the objfile is destroyed.
 349
 350      This is also used to work around a difference between the way gold
 351      generates .gdb_index version <=7 and the way gdb does.  Arguably this
 352      is a gold bug.  For symbols coming from TUs, gold records in the index
 353      the CU that includes the TU instead of the TU itself.  This breaks
 354      dw2_lookup_symbol: It assumes that if the index says symbol X lives
 355      in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
 356      will find X.  Alas TUs live in their own symtab, so after expanding CU Y
 357      we need to look in TU Z to find X.  Fortunately, this is akin to
 358      DW_TAG_imported_unit, so we just use the same mechanism: For
 359      .gdb_index version <=7 this also records the TUs that the CU referred
 360      to.  Concurrently with this change gdb was modified to emit version 8
 361      indices so we only pay a price for gold generated indices.
 362      http://sourceware.org/bugzilla/show_bug.cgi?id=15021.  */
 363   VEC (dwarf2_per_cu_ptr) *imported_symtabs;
 364 };
 365
 366 /* Entry in the signatured_types hash table.  */
 367
 368 struct signatured_type
 369 {
 370   /* The "per_cu" object of this type.
 371      This struct is used iff per_cu.is_debug_types.
 372      N.B.: This is the first member so that it's easy to convert pointers
 373      between them.  */
 374   struct dwarf2_per_cu_data per_cu;
 375
 376   /* The type's signature.  */
 377   ULONGEST signature;
 378
 379   /* Offset in the TU of the type's DIE, as read from the TU header.
 380      If this TU is a DWO stub and the definition lives in a DWO file
 381      (specified by DW_AT_GNU_dwo_name), this value is unusable.  */
 382   cu_offset type_offset_in_tu;
 383
 384   /* Offset in the section of the type's DIE.
 385      If the definition lives in a DWO file, this is the offset in the
 386      .debug_types.dwo section.
 387      The value is zero until the actual value is known.
 388      Zero is otherwise not a valid section offset.  */
 389   sect_offset type_offset_in_section;
 390
 391   /* Type units are grouped by their DW_AT_stmt_list entry so that they
 392      can share them.  This points to the containing symtab.  */
 393   struct type_unit_group *type_unit_group;
 394
 395   /* The type.
 396      The first time we encounter this type we fully read it in and install it
 397      in the symbol tables.  Subsequent times we only need the type.  */
 398   struct type *type;
 399
 400   /* Containing DWO unit.
 401      This field is valid iff per_cu.reading_dwo_directly.  */
 402   struct dwo_unit *dwo_unit;
 403 };
 404
 405 typedef struct signatured_type *sig_type_ptr;
 406 DEF_VEC_P (sig_type_ptr);
 407
 408 #endif /* DWARF2READ_H */