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