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