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/>. */
24 #include <unordered_map>
25 #include "dwarf2/index-cache.h"
26 #include "dwarf2/section.h"
27 #include "filename-seen-cache.h"
28 #include "gdb_obstack.h"
29 #include "gdbsupport/hash_enum.h"
32 /* Hold 'maintenance (set|show) dwarf' commands. */
33 extern struct cmd_list_element
*set_dwarf_cmdlist
;
34 extern struct cmd_list_element
*show_dwarf_cmdlist
;
38 int nr_uniq_abbrev_tables
;
40 int nr_symtab_sharers
;
41 int nr_stmt_less_type_units
;
42 int nr_all_type_units_reallocs
;
45 struct dwarf2_debug_sections
;
46 struct dwarf2_per_cu_data
;
48 struct mapped_debug_names
;
49 struct signatured_type
;
51 /* One item on the queue of compilation units to read in full symbols
53 struct dwarf2_queue_item
55 dwarf2_queue_item (dwarf2_per_cu_data
*cu
, dwarf2_per_objfile
*per_objfile
,
58 per_objfile (per_objfile
),
59 pretend_language (lang
)
63 ~dwarf2_queue_item ();
65 DISABLE_COPY_AND_ASSIGN (dwarf2_queue_item
);
67 dwarf2_per_cu_data
*per_cu
;
68 dwarf2_per_objfile
*per_objfile
;
69 enum language pretend_language
;
72 /* Some DWARF data can be shared across objfiles who share the same BFD,
73 this data is stored in this object.
75 Two dwarf2_per_objfile objects representing objfiles sharing the same BFD
76 will point to the same instance of dwarf2_per_bfd, unless the BFD requires
81 /* Construct a dwarf2_per_bfd for OBFD. NAMES points to the
82 dwarf2 section names, or is NULL if the standard ELF names are
83 used. CAN_COPY is true for formats where symbol
84 interposition is possible and so symbol values must follow copy
86 dwarf2_per_bfd (bfd
*obfd
, const dwarf2_debug_sections
*names
, bool can_copy
);
90 DISABLE_COPY_AND_ASSIGN (dwarf2_per_bfd
);
92 /* Return the CU/TU given its index.
94 This is intended for loops like:
96 for (i = 0; i < (dwarf2_per_bfd->n_comp_units
97 + dwarf2_per_bfd->n_type_units); ++i)
99 dwarf2_per_cu_data *per_cu = dwarf2_per_bfd->get_cutu (i);
104 dwarf2_per_cu_data
*get_cutu (int index
);
106 /* Return the CU given its index.
107 This differs from get_cutu in that it's for when you know INDEX refers to a
109 dwarf2_per_cu_data
*get_cu (int index
);
111 /* Return the TU given its index.
112 This differs from get_cutu in that it's for when you know INDEX refers to a
114 signatured_type
*get_tu (int index
);
116 /* Free all cached compilation units. */
117 void free_cached_comp_units ();
119 /* A convenience function to allocate a dwarf2_per_cu_data. The
120 returned object has its "index" field set properly. The object
121 is allocated on the dwarf2_per_bfd obstack. */
122 dwarf2_per_cu_data
*allocate_per_cu ();
124 /* A convenience function to allocate a signatured_type. The
125 returned object has its "index" field set properly. The object
126 is allocated on the dwarf2_per_bfd obstack. */
127 signatured_type
*allocate_signatured_type ();
129 /* Return the number of partial symtabs allocated with allocate_per_cu
130 and allocate_signatured_type so far. */
131 int num_psymtabs () const
132 { return m_num_psymtabs
; }
135 /* This function is mapped across the sections and remembers the
136 offset and size of each of the debugging sections we are
138 void locate_sections (bfd
*abfd
, asection
*sectp
,
139 const dwarf2_debug_sections
&names
);
142 /* The corresponding BFD. */
145 /* Objects that can be shared across objfiles are stored in this
146 obstack or on the psymtab obstack, while objects that are
147 objfile-specific are stored on the objfile obstack. */
148 auto_obstack obstack
;
150 dwarf2_section_info info
{};
151 dwarf2_section_info abbrev
{};
152 dwarf2_section_info line
{};
153 dwarf2_section_info loc
{};
154 dwarf2_section_info loclists
{};
155 dwarf2_section_info macinfo
{};
156 dwarf2_section_info macro
{};
157 dwarf2_section_info str
{};
158 dwarf2_section_info str_offsets
{};
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
{};
169 std::vector
<dwarf2_section_info
> types
;
171 /* Table of all the compilation units. This is used to locate
172 the target compilation unit of a particular reference. */
173 std::vector
<dwarf2_per_cu_data
*> all_comp_units
;
175 /* The .debug_types-related CUs (TUs). */
176 std::vector
<signatured_type
*> all_type_units
;
178 /* Table of struct type_unit_group objects.
179 The hash key is the DW_AT_stmt_list value. */
180 htab_up type_unit_groups
;
182 /* A table mapping .debug_types signatures to its signatured_type entry.
183 This is NULL if the .debug_types section hasn't been read in yet. */
184 htab_up signatured_types
;
186 /* Type unit statistics, to see how well the scaling improvements
188 struct tu_stats tu_stats
{};
190 /* A chain of compilation units that are currently read in, so that
191 they can be freed later. */
192 dwarf2_per_cu_data
*read_in_chain
= NULL
;
194 /* A table mapping DW_AT_dwo_name values to struct dwo_file objects.
195 This is NULL if the table hasn't been allocated yet. */
198 /* True if we've checked for whether there is a DWP file. */
199 bool dwp_checked
= false;
201 /* The DWP file if there is one, or NULL. */
202 std::unique_ptr
<struct dwp_file
> dwp_file
;
204 /* The shared '.dwz' file, if one exists. This is used when the
205 original data was compressed using 'dwz -m'. */
206 std::unique_ptr
<struct dwz_file
> dwz_file
;
208 /* Whether copy relocations are supported by this object format. */
211 /* A flag indicating whether this objfile has a section loaded at a
213 bool has_section_at_zero
= false;
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;
219 /* The mapped index, or NULL if .gdb_index is missing or not being used. */
220 std::unique_ptr
<mapped_index
> index_table
;
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
;
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_up quick_file_names_table
;
234 /* Set during partial symbol reading, to prevent queueing of full
236 bool reading_partial_symbols
= false;
238 /* The CUs we recently read. */
239 std::vector
<dwarf2_per_cu_data
*> just_read_cus
;
241 /* Table containing line_header indexed by offset and offset_in_dwz. */
242 htab_up line_header_hash
;
244 /* Table containing all filenames. This is an optional because the
245 table is lazily constructed on first access. */
246 gdb::optional
<filename_seen_cache
> filenames_cache
;
248 /* If we loaded the index from an external file, this contains the
249 resources associated to the open file, memory mapping, etc. */
250 std::unique_ptr
<index_cache_resource
> index_cache_res
;
252 /* Mapping from abstract origin DIE to concrete DIEs that reference it as
253 DW_AT_abstract_origin. */
254 std::unordered_map
<sect_offset
, std::vector
<sect_offset
>,
255 gdb::hash_enum
<sect_offset
>>
256 abstract_to_concrete
;
258 /* CUs that are queued to be read. */
259 std::queue
<dwarf2_queue_item
> queue
;
263 /* The total number of per_cu and signatured_type objects that have
264 been created so far for this reader. */
265 size_t m_num_psymtabs
= 0;
268 /* Collection of data recorded per objfile.
269 This hangs off of dwarf2_objfile_data_key.
271 Some DWARF data cannot (currently) be shared across objfiles. Such
272 data is stored in this object. */
274 struct dwarf2_per_objfile
276 dwarf2_per_objfile (struct objfile
*objfile
, dwarf2_per_bfd
*per_bfd
)
277 : objfile (objfile
), per_bfd (per_bfd
)
280 /* Return pointer to string at .debug_line_str offset as read from BUF.
281 BUF is assumed to be in a compilation unit described by CU_HEADER.
282 Return *BYTES_READ_PTR count of bytes read from BUF. */
283 const char *read_line_string (const gdb_byte
*buf
,
284 const struct comp_unit_head
*cu_header
,
285 unsigned int *bytes_read_ptr
);
287 /* Resize the M_SYMTABS vector to the needed size (the number of partial
288 symtabs allocated by the per-bfd). */
289 void resize_symtabs ()
291 /* The symtabs vector should only grow, not shrink. */
292 gdb_assert (per_bfd
->num_psymtabs () >= m_symtabs
.size ());
294 m_symtabs
.resize (per_bfd
->num_psymtabs ());
297 /* Return true if the symtab corresponding to PER_CU has been set,
299 bool symtab_set_p (const dwarf2_per_cu_data
*per_cu
) const;
301 /* Return the compunit_symtab associated to PER_CU, if it has been created. */
302 compunit_symtab
*get_symtab (const dwarf2_per_cu_data
*per_cu
) const;
304 /* Set the compunit_symtab associated to PER_CU. */
305 void set_symtab (const dwarf2_per_cu_data
*per_cu
, compunit_symtab
*symtab
);
307 /* Find an integer type SIZE_IN_BYTES bytes in size and return it.
308 UNSIGNED_P controls if the integer is unsigned or not. */
309 struct type
*int_type (int size_in_bytes
, bool unsigned_p
) const;
312 struct objfile
*objfile
;
314 /* Pointer to the data that is (possibly) shared between this objfile and
315 other objfiles backed by the same BFD. */
316 struct dwarf2_per_bfd
*per_bfd
;
318 /* Table mapping type DIEs to their struct type *.
319 This is nullptr if not allocated yet.
320 The mapping is done via (CU/TU + DIE offset) -> type. */
321 htab_up die_type_hash
;
324 /* Hold the corresponding compunit_symtab for each CU or TU. This
325 is indexed by dwarf2_per_cu_data::index. A NULL value means
326 that the CU/TU has not been expanded yet. */
327 std::vector
<compunit_symtab
*> m_symtabs
;
330 /* Get the dwarf2_per_objfile associated to OBJFILE. */
332 dwarf2_per_objfile
*get_dwarf2_per_objfile (struct objfile
*objfile
);
334 /* A partial symtab specialized for DWARF. */
335 struct dwarf2_psymtab
: public partial_symtab
337 dwarf2_psymtab (const char *filename
, struct objfile
*objfile
,
338 dwarf2_per_cu_data
*per_cu
)
339 : partial_symtab (filename
, objfile
, 0),
344 void read_symtab (struct objfile
*) override
;
345 void expand_psymtab (struct objfile
*) override
;
346 bool readin_p (struct objfile
*) const override
;
347 compunit_symtab
*get_compunit_symtab (struct objfile
*) const override
;
349 struct dwarf2_per_cu_data
*per_cu_data
;
352 /* Persistent data held for a compilation unit, even when not
353 processing it. We put a pointer to this structure in the
356 struct dwarf2_per_cu_data
358 /* The start offset and length of this compilation unit.
359 NOTE: Unlike comp_unit_head.length, this length includes
361 If the DIE refers to a DWO file, this is always of the original die,
363 sect_offset sect_off
;
366 /* DWARF standard version this data has been read from (such as 4 or 5). */
369 /* Flag indicating this compilation unit will be read in before
370 any of the current compilation units are processed. */
371 unsigned int queued
: 1;
373 /* This flag will be set when reading partial DIEs if we need to load
374 absolutely all DIEs for this compilation unit, instead of just the ones
375 we think are interesting. It gets set if we look for a DIE in the
376 hash table and don't find it. */
377 unsigned int load_all_dies
: 1;
379 /* Non-zero if this CU is from .debug_types.
380 Struct dwarf2_per_cu_data is contained in struct signatured_type iff
382 unsigned int is_debug_types
: 1;
384 /* Non-zero if this CU is from the .dwz file. */
385 unsigned int is_dwz
: 1;
387 /* Non-zero if reading a TU directly from a DWO file, bypassing the stub.
388 This flag is only valid if is_debug_types is true.
389 We can't read a CU directly from a DWO file: There are required
390 attributes in the stub. */
391 unsigned int reading_dwo_directly
: 1;
393 /* Non-zero if the TU has been read.
394 This is used to assist the "Stay in DWO Optimization" for Fission:
395 When reading a DWO, it's faster to read TUs from the DWO instead of
396 fetching them from random other DWOs (due to comdat folding).
397 If the TU has already been read, the optimization is unnecessary
398 (and unwise - we don't want to change where gdb thinks the TU lives
400 This flag is only valid if is_debug_types is true. */
401 unsigned int tu_read
: 1;
403 /* Our index in the unshared "symtabs" vector. */
406 /* The section this CU/TU lives in.
407 If the DIE refers to a DWO file, this is always the original die,
409 struct dwarf2_section_info
*section
;
411 /* Set to non-NULL iff this CU is currently loaded. When it gets freed out
412 of the CU cache it gets reset to NULL again. This is left as NULL for
413 dummy CUs (a CU header, but nothing else). */
414 struct dwarf2_cu
*cu
;
416 /* The unit type of this CU. */
417 enum dwarf_unit_type unit_type
;
419 /* The language of this CU. */
422 /* The corresponding dwarf2_per_objfile. */
423 struct dwarf2_per_objfile
*dwarf2_per_objfile
;
425 /* Backlink to the owner of this. */
426 dwarf2_per_bfd
*per_bfd
;
428 /* When dwarf2_per_bfd::using_index is true, the 'quick' field
429 is active. Otherwise, the 'psymtab' field is active. */
432 /* The partial symbol table associated with this compilation unit,
433 or NULL for unread partial units. */
434 dwarf2_psymtab
*psymtab
;
436 /* Data needed by the "quick" functions. */
437 struct dwarf2_per_cu_quick_data
*quick
;
440 /* The CUs we import using DW_TAG_imported_unit. This is filled in
441 while reading psymtabs, used to compute the psymtab dependencies,
442 and then cleared. Then it is filled in again while reading full
443 symbols, and only deleted when the objfile is destroyed.
445 This is also used to work around a difference between the way gold
446 generates .gdb_index version <=7 and the way gdb does. Arguably this
447 is a gold bug. For symbols coming from TUs, gold records in the index
448 the CU that includes the TU instead of the TU itself. This breaks
449 dw2_lookup_symbol: It assumes that if the index says symbol X lives
450 in CU/TU Y, then one need only expand Y and a subsequent lookup in Y
451 will find X. Alas TUs live in their own symtab, so after expanding CU Y
452 we need to look in TU Z to find X. Fortunately, this is akin to
453 DW_TAG_imported_unit, so we just use the same mechanism: For
454 .gdb_index version <=7 this also records the TUs that the CU referred
455 to. Concurrently with this change gdb was modified to emit version 8
456 indices so we only pay a price for gold generated indices.
457 http://sourceware.org/bugzilla/show_bug.cgi?id=15021.
459 This currently needs to be a public member due to how
460 dwarf2_per_cu_data is allocated and used. Ideally in future things
461 could be refactored to make this private. Until then please try to
462 avoid direct access to this member, and instead use the helper
464 std::vector
<dwarf2_per_cu_data
*> *imported_symtabs
;
466 /* Return true of IMPORTED_SYMTABS is empty or not yet allocated. */
467 bool imported_symtabs_empty () const
469 return (imported_symtabs
== nullptr || imported_symtabs
->empty ());
472 /* Push P to the back of IMPORTED_SYMTABS, allocated IMPORTED_SYMTABS
473 first if required. */
474 void imported_symtabs_push (dwarf2_per_cu_data
*p
)
476 if (imported_symtabs
== nullptr)
477 imported_symtabs
= new std::vector
<dwarf2_per_cu_data
*>;
478 imported_symtabs
->push_back (p
);
481 /* Return the size of IMPORTED_SYMTABS if it is allocated, otherwise
483 size_t imported_symtabs_size () const
485 if (imported_symtabs
== nullptr)
487 return imported_symtabs
->size ();
490 /* Delete IMPORTED_SYMTABS and set the pointer back to nullptr. */
491 void imported_symtabs_free ()
493 delete imported_symtabs
;
494 imported_symtabs
= nullptr;
497 /* Return the address size given in the compilation unit header for
499 int addr_size () const;
501 /* Return the offset size given in the compilation unit header for
503 int offset_size () const;
505 /* Return the DW_FORM_ref_addr size given in the compilation unit
506 header for this CU. */
507 int ref_addr_size () const;
509 /* Return DWARF version number of this CU. */
510 short version () const
512 return dwarf_version
;
515 /* A type unit group has a per_cu object that is recognized by
516 having no section. */
517 bool type_unit_group_p () const
519 return section
== nullptr;
523 /* Entry in the signatured_types hash table. */
525 struct signatured_type
527 /* The "per_cu" object of this type.
528 This struct is used iff per_cu.is_debug_types.
529 N.B.: This is the first member so that it's easy to convert pointers
531 struct dwarf2_per_cu_data per_cu
;
533 /* The type's signature. */
536 /* Offset in the TU of the type's DIE, as read from the TU header.
537 If this TU is a DWO stub and the definition lives in a DWO file
538 (specified by DW_AT_GNU_dwo_name), this value is unusable. */
539 cu_offset type_offset_in_tu
;
541 /* Offset in the section of the type's DIE.
542 If the definition lives in a DWO file, this is the offset in the
543 .debug_types.dwo section.
544 The value is zero until the actual value is known.
545 Zero is otherwise not a valid section offset. */
546 sect_offset type_offset_in_section
;
548 /* Type units are grouped by their DW_AT_stmt_list entry so that they
549 can share them. This points to the containing symtab. */
550 struct type_unit_group
*type_unit_group
;
553 The first time we encounter this type we fully read it in and install it
554 in the symbol tables. Subsequent times we only need the type. */
557 /* Containing DWO unit.
558 This field is valid iff per_cu.reading_dwo_directly. */
559 struct dwo_unit
*dwo_unit
;
562 /* Open the separate '.dwz' debug file, if needed. Return NULL if
563 there is no .gnu_debugaltlink section in the file. Error if there
564 is such a section but the file cannot be found. */
566 extern dwz_file
*dwarf2_get_dwz_file (dwarf2_per_bfd
*per_bfd
);
568 /* Return the type of the DIE at DIE_OFFSET in the CU named by
571 struct type
*dwarf2_get_die_type (cu_offset die_offset
,
572 struct dwarf2_per_cu_data
*per_cu
);
574 /* Given an index in .debug_addr, fetch the value.
575 NOTE: This can be called during dwarf expression evaluation,
576 long after the debug information has been read, and thus per_cu->cu
577 may no longer exist. */
579 CORE_ADDR
dwarf2_read_addr_index (dwarf2_per_cu_data
*per_cu
,
580 dwarf2_per_objfile
*dwarf2_per_objfile
,
581 unsigned int addr_index
);
583 /* Return DWARF block referenced by DW_AT_location of DIE at SECT_OFF at PER_CU.
584 Returned value is intended for DW_OP_call*. Returned
585 dwarf2_locexpr_baton->data has lifetime of
586 PER_CU->DWARF2_PER_OBJFILE->OBJFILE. */
588 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_sect_off
589 (sect_offset sect_off
, dwarf2_per_cu_data
*per_cu
,
590 dwarf2_per_objfile
*per_objfile
,
591 CORE_ADDR (*get_frame_pc
) (void *baton
),
592 void *baton
, bool resolve_abstract_p
= false);
594 /* Like dwarf2_fetch_die_loc_sect_off, but take a CU
597 struct dwarf2_locexpr_baton dwarf2_fetch_die_loc_cu_off
598 (cu_offset offset_in_cu
, dwarf2_per_cu_data
*per_cu
,
599 dwarf2_per_objfile
*per_objfile
,
600 CORE_ADDR (*get_frame_pc
) (void *baton
),
603 /* If the DIE at SECT_OFF in PER_CU has a DW_AT_const_value, return a
604 pointer to the constant bytes and set LEN to the length of the
605 data. If memory is needed, allocate it on OBSTACK. If the DIE
606 does not have a DW_AT_const_value, return NULL. */
608 extern const gdb_byte
*dwarf2_fetch_constant_bytes
609 (sect_offset sect_off
, dwarf2_per_cu_data
*per_cu
,
610 dwarf2_per_objfile
*per_objfile
, obstack
*obstack
,
613 /* Return the type of the die at SECT_OFF in PER_CU. Return NULL if no
614 valid type for this die is found. */
616 struct type
*dwarf2_fetch_die_type_sect_off
617 (sect_offset sect_off
, dwarf2_per_cu_data
*per_cu
,
618 dwarf2_per_objfile
*per_objfile
);
620 /* When non-zero, dump line number entries as they are read in. */
621 extern unsigned int dwarf_line_debug
;
623 #endif /* DWARF2READ_H */