1 /* DWARF 2 debugging format support for GDB.
3 Copyright (C) 1994-2020 Free Software Foundation, Inc.
5 This file is part of GDB.
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.
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.
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/>. */
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"
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
;
33 extern bool dwarf_always_disassemble
;
35 /* A descriptor for dwarf sections.
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.
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
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. */
51 struct dwarf2_section_info
55 /* If this is a real section, the bfd section. */
57 /* If this is a virtual section, pointer to the containing ("real")
59 struct dwarf2_section_info
*containing_section
;
61 /* Pointer to section data, only valid if readin. */
62 const gdb_byte
*buffer
;
63 /* The size of the section, real or virtual. */
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. */
70 /* True if this is a virtual section, False otherwise.
71 This specifies which of s.section and s.containing_section to use. */
75 /* Read the contents of the section INFO.
76 OBJFILE is the main object file, but not necessarily the file where
77 the section comes from. E.g., for DWO files the bfd of INFO is the bfd
79 If the section is compressed, uncompress it before returning. */
81 void dwarf2_read_section (struct objfile
*objfile
, dwarf2_section_info
*info
);
85 int nr_uniq_abbrev_tables
;
87 int nr_symtab_sharers
;
88 int nr_stmt_less_type_units
;
89 int nr_all_type_units_reallocs
;
92 struct dwarf2_debug_sections
;
94 struct mapped_debug_names
;
95 struct signatured_type
;
97 typedef struct die_info
*die_info_ptr
;
99 /* Collection of data recorded per objfile.
100 This hangs off of dwarf2_objfile_data_key. */
102 struct dwarf2_per_objfile
104 /* Construct a dwarf2_per_objfile for OBJFILE. NAMES points to the
105 dwarf2 section names, or is NULL if the standard ELF names are
106 used. CAN_COPY is true for formats where symbol
107 interposition is possible and so symbol values must follow copy
109 dwarf2_per_objfile (struct objfile
*objfile
,
110 const dwarf2_debug_sections
*names
,
113 ~dwarf2_per_objfile ();
115 DISABLE_COPY_AND_ASSIGN (dwarf2_per_objfile
);
117 /* Return the CU/TU given its index.
119 This is intended for loops like:
121 for (i = 0; i < (dwarf2_per_objfile->n_comp_units
122 + dwarf2_per_objfile->n_type_units); ++i)
124 dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);
129 dwarf2_per_cu_data
*get_cutu (int index
);
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
134 dwarf2_per_cu_data
*get_cu (int index
);
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
139 signatured_type
*get_tu (int index
);
141 /* Free all cached compilation units. */
142 void free_cached_comp_units ();
144 /* This function is mapped across the sections and remembers the
145 offset and size of each of the debugging sections we are
147 void locate_sections (bfd
*abfd
, asection
*sectp
,
148 const dwarf2_debug_sections
&names
);
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 str_offsets
{};
160 dwarf2_section_info line_str
{};
161 dwarf2_section_info ranges
{};
162 dwarf2_section_info rnglists
{};
163 dwarf2_section_info addr
{};
164 dwarf2_section_info frame
{};
165 dwarf2_section_info eh_frame
{};
166 dwarf2_section_info gdb_index
{};
167 dwarf2_section_info debug_names
{};
168 dwarf2_section_info debug_aranges
{};
170 std::vector
<dwarf2_section_info
> types
;
173 struct objfile
*objfile
= NULL
;
175 /* Table of all the compilation units. This is used to locate
176 the target compilation unit of a particular reference. */
177 std::vector
<dwarf2_per_cu_data
*> all_comp_units
;
179 /* The .debug_types-related CUs (TUs). */
180 std::vector
<signatured_type
*> all_type_units
;
182 /* Table of struct type_unit_group objects.
183 The hash key is the DW_AT_stmt_list value. */
184 htab_t type_unit_groups
{};
186 /* A table mapping .debug_types signatures to its signatured_type entry.
187 This is NULL if the .debug_types section hasn't been read in yet. */
188 htab_t signatured_types
{};
190 /* Type unit statistics, to see how well the scaling improvements
192 struct tu_stats tu_stats
{};
194 /* A chain of compilation units that are currently read in, so that
195 they can be freed later. */
196 dwarf2_per_cu_data
*read_in_chain
= NULL
;
198 /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
199 This is NULL if the table hasn't been allocated yet. */
202 /* True if we've checked for whether there is a DWP file. */
203 bool dwp_checked
= false;
205 /* The DWP file if there is one, or NULL. */
206 std::unique_ptr
<struct dwp_file
> dwp_file
;
208 /* The shared '.dwz' file, if one exists. This is used when the
209 original data was compressed using 'dwz -m'. */
210 std::unique_ptr
<struct dwz_file
> dwz_file
;
212 /* Whether copy relocations are supported by this object format. */
215 /* A flag indicating whether this objfile has a section loaded at a
217 bool has_section_at_zero
= false;
219 /* True if we are using the mapped index,
220 or we are faking it for OBJF_READNOW's sake. */
221 bool using_index
= false;
223 /* The mapped index, or NULL if .gdb_index is missing or not being used. */
224 std::unique_ptr
<mapped_index
> index_table
;
226 /* The mapped index, or NULL if .debug_names is missing or not being used. */
227 std::unique_ptr
<mapped_debug_names
> debug_names_table
;
229 /* When using index_table, this keeps track of all quick_file_names entries.
230 TUs typically share line table entries with a CU, so we maintain a
231 separate table of all line table entries to support the sharing.
232 Note that while there can be way more TUs than CUs, we've already
233 sorted all the TUs into "type unit groups", grouped by their
234 DW_AT_stmt_list value. Therefore the only sharing done here is with a
235 CU and its associated TU group if there is one. */
236 htab_t quick_file_names_table
{};
238 /* Set during partial symbol reading, to prevent queueing of full
240 bool reading_partial_symbols
= false;
242 /* Table mapping type DIEs to their struct type *.
243 This is NULL if not allocated yet.
244 The mapping is done via (CU/TU + DIE offset) -> type. */
245 htab_t die_type_hash
{};
247 /* The CUs we recently read. */
248 std::vector
<dwarf2_per_cu_data
*> just_read_cus
;
250 /* Table containing line_header indexed by offset and offset_in_dwz. */
251 htab_t line_header_hash
{};
253 /* Table containing all filenames. This is an optional because the
254 table is lazily constructed on first access. */
255 gdb::optional
<filename_seen_cache
> filenames_cache
;
257 /* If we loaded the index from an external file, this contains the
258 resources associated to the open file, memory mapping, etc. */
259 std::unique_ptr
<index_cache_resource
> index_cache_res
;
261 /* Mapping from abstract origin DIE to concrete DIEs that reference it as
262 DW_AT_abstract_origin. */
263 std::unordered_map
<sect_offset
, std::vector
<sect_offset
>,
264 gdb::hash_enum
<sect_offset
>>
265 abstract_to_concrete
;
268 /* Get the dwarf2_per_objfile associated to OBJFILE. */
270 dwarf2_per_objfile
*get_dwarf2_per_objfile (struct objfile
*objfile
);
272 /* Persistent data held for a compilation unit, even when not
273 processing it. We put a pointer to this structure in the
274 read_symtab_private field of the psymtab. */
276 struct dwarf2_per_cu_data
278 /* The start offset and length of this compilation unit.
279 NOTE: Unlike comp_unit_head.length, this length includes
281 If the DIE refers to a DWO file, this is always of the original die,
283 sect_offset sect_off
;
286 /* DWARF standard version this data has been read from (such as 4 or 5). */
289 /* Flag indicating this compilation unit will be read in before
290 any of the current compilation units are processed. */
291 unsigned int queued
: 1;
293 /* This flag will be set when reading partial DIEs if we need to load
294 absolutely all DIEs for this compilation unit, instead of just the ones
295 we think are interesting. It gets set if we look for a DIE in the
296 hash table and don't find it. */
297 unsigned int load_all_dies
: 1;
299 /* Non-zero if this CU is from .debug_types.
300 Struct dwarf2_per_cu_data is contained in struct signatured_type iff
302 unsigned int is_debug_types
: 1;
304 /* Non-zero if this CU is from the .dwz file. */
305 unsigned int is_dwz
: 1;
307 /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
308 This flag is only valid if is_debug_types is true.
309 We can't read a CU directly from a DWO file: There are required
310 attributes in the stub. */
311 unsigned int reading_dwo_directly
: 1;
313 /* Non-zero if the TU has been read.
314 This is used to assist the "Stay in DWO Optimization" for Fission:
315 When reading a DWO, it's faster to read TUs from the DWO instead of
316 fetching them from random other DWOs (due to comdat folding).
317 If the TU has already been read, the optimization is unnecessary
318 (and unwise - we don't want to change where gdb thinks the TU lives
320 This flag is only valid if is_debug_types is true. */
321 unsigned int tu_read
: 1;
323 /* The section this CU/TU lives in.
324 If the DIE refers to a DWO file, this is always the original die,
326 struct dwarf2_section_info
*section
;
328 /* Set to non-NULL iff this CU is currently loaded. When it gets freed out
329 of the CU cache it gets reset to NULL again. This is left as NULL for
330 dummy CUs (a CU header, but nothing else). */
331 struct dwarf2_cu
*cu
;
333 /* The corresponding dwarf2_per_objfile. */
334 struct dwarf2_per_objfile
*dwarf2_per_objfile
;
336 /* When dwarf2_per_objfile->using_index is true, the 'quick' field
337 is active. Otherwise, the 'psymtab' field is active. */
340 /* The partial symbol table associated with this compilation unit,
341 or NULL for unread partial units. */
342 struct partial_symtab
*psymtab
;
344 /* Data needed by the "quick" functions. */
345 struct dwarf2_per_cu_quick_data
*quick
;
348 /* Return true of IMPORTED_SYMTABS is empty or not yet allocated. */
349 bool imported_symtabs_empty () const
351 return (imported_symtabs
== nullptr || imported_symtabs
->empty ());
354 /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
355 first if required. */
356 void imported_symtabs_push (dwarf2_per_cu_data
*p
)
358 if (imported_symtabs
== nullptr)
359 imported_symtabs
= new std::vector
<dwarf2_per_cu_data
*>;
360 imported_symtabs
->push_back (p
);
363 /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
365 size_t imported_symtabs_size () const
367 if (imported_symtabs
== nullptr)
369 return imported_symtabs
->size ();
372 /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr. */
373 void imported_symtabs_free ()
375 delete imported_symtabs
;
376 imported_symtabs
= nullptr;
379 /* The CUs we import using DW_TAG_imported_unit. This is filled in
380 while reading psymtabs, used to compute the psymtab dependencies,
381 and then cleared. Then it is filled in again while reading full
382 symbols, and only deleted when the objfile is destroyed.
384 This is also used to work around a difference between the way gold
385 generates .gdb_index version <=7 and the way gdb does. Arguably this
386 is a gold bug. For symbols coming from TUs, gold records in the index
387 the CU that includes the TU instead of the TU itself. This breaks
388 dw2_lookup_symbol: It assumes that if the index says symbol X lives
389 in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
390 will find X. Alas TUs live in their own symtab, so after expanding CU Y
391 we need to look in TU Z to find X. Fortunately, this is akin to
392 DW_TAG_imported_unit, so we just use the same mechanism: For
393 .gdb_index version <=7 this also records the TUs that the CU referred
394 to. Concurrently with this change gdb was modified to emit version 8
395 indices so we only pay a price for gold generated indices.
396 http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
398 This currently needs to be a public member due to how
399 dwarf2_per_cu_data is allocated and used. Ideally in future things
400 could be refactored to make this private. Until then please try to
401 avoid direct access to this member, and instead use the helper
403 std::vector
<dwarf2_per_cu_data
*> *imported_symtabs
;
406 /* Entry in the signatured_types hash table. */
408 struct signatured_type
410 /* The "per_cu" object of this type.
411 This struct is used iff per_cu.is_debug_types.
412 N.B.: This is the first member so that it's easy to convert pointers
414 struct dwarf2_per_cu_data per_cu
;
416 /* The type's signature. */
419 /* Offset in the TU of the type's DIE, as read from the TU header.
420 If this TU is a DWO stub and the definition lives in a DWO file
421 (specified by DW_AT_GNU_dwo_name), this value is unusable. */
422 cu_offset type_offset_in_tu
;
424 /* Offset in the section of the type's DIE.
425 If the definition lives in a DWO file, this is the offset in the
426 .debug_types.dwo section.
427 The value is zero until the actual value is known.
428 Zero is otherwise not a valid section offset. */
429 sect_offset type_offset_in_section
;
431 /* Type units are grouped by their DW_AT_stmt_list entry so that they
432 can share them. This points to the containing symtab. */
433 struct type_unit_group
*type_unit_group
;
436 The first time we encounter this type we fully read it in and install it
437 in the symbol tables. Subsequent times we only need the type. */
440 /* Containing DWO unit.
441 This field is valid iff per_cu.reading_dwo_directly. */
442 struct dwo_unit
*dwo_unit
;
445 ULONGEST
read_unsigned_leb128 (bfd
*, const gdb_byte
*, unsigned int *);
447 /* This represents a '.dwz' file. */
451 dwz_file (gdb_bfd_ref_ptr
&&bfd
)
452 : dwz_bfd (std::move (bfd
))
456 const char *filename () const
458 return bfd_get_filename (this->dwz_bfd
.get ());
461 /* A dwz file can only contain a few sections. */
462 struct dwarf2_section_info abbrev
{};
463 struct dwarf2_section_info info
{};
464 struct dwarf2_section_info str
{};
465 struct dwarf2_section_info line
{};
466 struct dwarf2_section_info macro
{};
467 struct dwarf2_section_info gdb_index
{};
468 struct dwarf2_section_info debug_names
{};
471 gdb_bfd_ref_ptr dwz_bfd
;
473 /* If we loaded the index from an external file, this contains the
474 resources associated to the open file, memory mapping, etc. */
475 std::unique_ptr
<index_cache_resource
> index_cache_res
;
478 /* Open the separate '.dwz' debug file, if needed. Return NULL if
479 there is no .gnu_debugaltlink section in the file. Error if there
480 is such a section but the file cannot be found. */
482 extern struct dwz_file
*dwarf2_get_dwz_file
483 (struct dwarf2_per_objfile
*dwarf2_per_objfile
);
485 #endif /* DWARF2READ_H */