[PATCH v2 01/42] Introduce dwarf2_per_objfile::obstack

Simon Marchi
2020-05-12T21:09:17Z

From: Tom Tromey <tom@tromey.com>

Currently much of the DWARF-related data is stored on the objfile
obstack. This prevents sharing this data across objfiles, so this patch
adds a new obstack to dwarf2_per_objfile. Note that the
dwarf2_per_objfile type is going to become "dwarf2_per_bfd" in a
subsequent patch, which is indeed going to be shared between objfiles.

One way to check whether this is correct is to look at the remaining
uses of objfile_obstack in the DWARF code and note that they all
appear in the "full CU" code paths.

The converse -- storing per-objfile data on the shared obstack -- is
not good, but it is just a memory leak, not a potential
use-after-free. Double-checking this would also be useful, though.

2020-02-21 Tom Tromey <tom@tromey.com>

* dwarf2/read.h (struct dwarf2_per_objfile) <obstack>: New
member.
* dwarf2/read.c (delete_file_name_entry): Fix comment.
(create_cu_from_index_list)
(create_signatured_type_table_from_index)
(create_signatured_type_table_from_debug_names)
(dw2_get_file_names_reader, dwarf2_initialize_objfile)
(dwarf2_create_include_psymtab)
(create_debug_type_hash_table, add_type_unit)
(create_type_unit_group, read_comp_units_from_section)
(dwarf2_compute_name, create_cus_hash_table)
(create_dwp_hash_table, create_dwo_unit_in_dwp_v1)
(create_dwo_unit_in_dwp_v2, open_and_init_dwp_file): Use new
obstack.
(dw2_get_real_path): Likewise. Change argument to
dwarf2_per_objfile.
---
gdb/dwarf2/read.c | 94 +++++++++++++++++++++--------------------------
gdb/dwarf2/read.h | 5 +++
2 files changed, 47 insertions(+), 52 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 27bf40a898d..0c28fd2cfc7 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2276,8 +2276,8 @@ delete_file_name_entry (void *e)
xfree ((void*) file_data->real_names[i]);
}

- /* The space for the struct itself lives on objfile_obstack,
- so we don't free it here. */
+ /* The space for the struct itself lives on the obstack, so we don't
+ free it here. */
}

/* Create a quick_file_names hash table. */
@@ -2408,9 +2408,8 @@ dwarf2_per_objfile::get_tu (int index)
return this->all_type_units[index];
}

-/* Return a new dwarf2_per_cu_data allocated on OBJFILE's
- objfile_obstack, and constructed with the specified field
- values. */
+/* Return a new dwarf2_per_cu_data allocated on the dwarf2_per_objfile
+ obstack, and constructed with the specified field values. */

static dwarf2_per_cu_data *
create_cu_from_index_list (struct dwarf2_per_objfile *dwarf2_per_objfile,
@@ -2418,16 +2417,15 @@ create_cu_from_index_list (struct dwarf2_per_objfile *dwarf2_per_objfile,
int is_dwz,
sect_offset sect_off, ULONGEST length)
{
- struct objfile *objfile = dwarf2_per_objfile->objfile;
dwarf2_per_cu_data *the_cu
- = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_data);
the_cu->sect_off = sect_off;
the_cu->length = length;
the_cu->dwarf2_per_objfile = dwarf2_per_objfile;
the_cu->section = section;
- the_cu->v.quick = OBSTACK_ZALLOC (&objfile->objfile_obstack,
- struct dwarf2_per_cu_quick_data);
+ the_cu->v.quick = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
+ struct dwarf2_per_cu_quick_data);
the_cu->is_dwz = is_dwz;
return the_cu;
}
@@ -2489,8 +2487,6 @@ create_signatured_type_table_from_index
const gdb_byte *bytes,
offset_type elements)
{
- struct objfile *objfile = dwarf2_per_objfile->objfile;
-
gdb_assert (dwarf2_per_objfile->all_type_units.empty ());
dwarf2_per_objfile->all_type_units.reserve (elements / 3);

@@ -2512,7 +2508,7 @@ create_signatured_type_table_from_index
signature = extract_unsigned_integer (bytes + 16, 8, BFD_ENDIAN_LITTLE);
bytes += 3 * 8;

- sig_type = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct signatured_type);
sig_type->signature = signature;
sig_type->type_offset_in_tu = type_offset_in_tu;
@@ -2521,7 +2517,7 @@ create_signatured_type_table_from_index
sig_type->per_cu.sect_off = sect_off;
sig_type->per_cu.dwarf2_per_objfile = dwarf2_per_objfile;
sig_type->per_cu.v.quick
- = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_quick_data);

slot = htab_find_slot (sig_types_hash.get (), sig_type, INSERT);
@@ -2569,7 +2565,7 @@ create_signatured_type_table_from_debug_names
section->buffer + to_underlying (sect_off),
rcuh_kind::TYPE);

- sig_type = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct signatured_type);
sig_type->signature = cu_header.signature;
sig_type->type_offset_in_tu = cu_header.type_cu_offset_in_tu;
@@ -2578,7 +2574,7 @@ create_signatured_type_table_from_debug_names
sig_type->per_cu.sect_off = sect_off;
sig_type->per_cu.dwarf2_per_objfile = dwarf2_per_objfile;
sig_type->per_cu.v.quick
- = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_quick_data);

slot = htab_find_slot (sig_types_hash.get (), sig_type, INSERT);
@@ -3088,7 +3084,6 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
struct dwarf2_per_cu_data *this_cu = cu->per_cu;
struct dwarf2_per_objfile *dwarf2_per_objfile
= cu->per_cu->dwarf2_per_objfile;
- struct objfile *objfile = dwarf2_per_objfile->objfile;
struct dwarf2_per_cu_data *lh_cu;
struct attribute *attr;
void **slot;
@@ -3137,7 +3132,7 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
return;
}

- qfn = XOBNEW (&objfile->objfile_obstack, struct quick_file_names);
+ qfn = XOBNEW (&dwarf2_per_objfile->obstack, struct quick_file_names);
qfn->hash.dwo_unit = cu->dwo_unit;
qfn->hash.line_sect_off = line_offset;
gdb_assert (slot != NULL);
@@ -3151,7 +3146,8 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,

qfn->num_file_names = offset + lh->file_names_size ();
qfn->file_names =
- XOBNEWVEC (&objfile->objfile_obstack, const char *, qfn->num_file_names);
+ XOBNEWVEC (&dwarf2_per_objfile->obstack, const char *,
+ qfn->num_file_names);
if (offset != 0)
qfn->file_names[0] = xstrdup (fnd.name);
for (int i = 0; i < lh->file_names_size (); ++i)
@@ -3192,11 +3188,11 @@ dw2_get_file_names (struct dwarf2_per_cu_data *this_cu)
real path for a given file name from the line table. */

static const char *
-dw2_get_real_path (struct objfile *objfile,
+dw2_get_real_path (struct dwarf2_per_objfile *dwarf2_per_objfile,
struct quick_file_names *qfn, int index)
{
if (qfn->real_names == NULL)
- qfn->real_names = OBSTACK_CALLOC (&objfile->objfile_obstack,
+ qfn->real_names = OBSTACK_CALLOC (&dwarf2_per_objfile->obstack,
qfn->num_file_names, const char *);

if (qfn->real_names[index] == NULL)
@@ -3316,7 +3312,8 @@ dw2_map_symtabs_matching_filename
&& FILENAME_CMP (lbasename (this_name), name_basename) != 0)
continue;

- this_real_name = dw2_get_real_path (objfile, file_data, j);
+ this_real_name = dw2_get_real_path (dwarf2_per_objfile,
+ file_data, j);
if (compare_filenames_for_search (this_real_name, name))
{
if (dw2_map_expand_apply (objfile, per_cu, name, real_path,
@@ -4563,8 +4560,6 @@ dw_expand_symtabs_matching_file_matcher
if (file_matcher == NULL)
return;

- objfile *const objfile = dwarf2_per_objfile->objfile;
-
htab_up visited_found (htab_create_alloc (10, htab_hash_pointer,
htab_eq_pointer,
NULL, xcalloc, xfree));
@@ -4614,7 +4609,8 @@ dw_expand_symtabs_matching_file_matcher
true))
continue;

- this_real_name = dw2_get_real_path (objfile, file_data, j);
+ this_real_name = dw2_get_real_path (dwarf2_per_objfile,
+ file_data, j);
if (file_matcher (this_real_name, false))
{
per_cu->v.quick->mark = 1;
@@ -5837,7 +5833,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
{
dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->get_cutu (i);

- per_cu->v.quick = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ per_cu->v.quick = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_quick_data);
}

@@ -6038,10 +6034,7 @@ dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
dwarf2_include_psymtab *subpst = new dwarf2_include_psymtab (name, objfile);

if (!IS_ABSOLUTE_PATH (subpst->filename))
- {
- /* It shares objfile->objfile_obstack. */
- subpst->dirname = pst->dirname;
- }
+ subpst->dirname = pst->dirname;

subpst->dependencies = objfile->partial_symtabs->allocate_dependencies (1);
subpst->dependencies[0] = pst;
@@ -6199,7 +6192,7 @@ create_debug_type_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
if (dwo_file)
{
sig_type = NULL;
- dwo_tu = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ dwo_tu = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwo_unit);
dwo_tu->dwo_file = dwo_file;
dwo_tu->signature = header.signature;
@@ -6213,7 +6206,7 @@ create_debug_type_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
/* N.B.: type_offset is not usable if this type uses a DWO file.
The real type_offset is in the DWO file. */
dwo_tu = NULL;
- sig_type = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct signatured_type);
sig_type->signature = header.signature;
sig_type->type_offset_in_tu = header.type_cu_offset_in_tu;
@@ -6325,13 +6318,11 @@ static struct signatured_type *
add_type_unit (struct dwarf2_per_objfile *dwarf2_per_objfile, ULONGEST sig,
void **slot)
{
- struct objfile *objfile = dwarf2_per_objfile->objfile;
-
if (dwarf2_per_objfile->all_type_units.size ()
== dwarf2_per_objfile->all_type_units.capacity ())
++dwarf2_per_objfile->tu_stats.nr_all_type_units_reallocs;

- signatured_type *sig_type = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ signatured_type *sig_type = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct signatured_type);

dwarf2_per_objfile->all_type_units.push_back (sig_type);
@@ -6340,7 +6331,7 @@ add_type_unit (struct dwarf2_per_objfile *dwarf2_per_objfile, ULONGEST sig,
if (dwarf2_per_objfile->using_index)
{
sig_type->per_cu.v.quick =
- OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_quick_data);
}

@@ -7198,18 +7189,17 @@ create_type_unit_group (struct dwarf2_cu *cu, sect_offset line_offset_struct)
{
struct dwarf2_per_objfile *dwarf2_per_objfile
= cu->per_cu->dwarf2_per_objfile;
- struct objfile *objfile = dwarf2_per_objfile->objfile;
struct dwarf2_per_cu_data *per_cu;
struct type_unit_group *tu_group;

- tu_group = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ tu_group = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct type_unit_group);
per_cu = &tu_group->per_cu;
per_cu->dwarf2_per_objfile = dwarf2_per_objfile;

if (dwarf2_per_objfile->using_index)
{
- per_cu->v.quick = OBSTACK_ZALLOC (&objfile->objfile_obstack,
+ per_cu->v.quick = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_quick_data);
}
else
@@ -7939,13 +7929,13 @@ read_comp_units_from_section (struct dwarf2_per_objfile *dwarf2_per_objfile,
/* Save the compilation unit for later lookup. */
if (cu_header.unit_type != DW_UT_type)
{
- this_cu = XOBNEW (&objfile->objfile_obstack,
+ this_cu = XOBNEW (&dwarf2_per_objfile->obstack,
struct dwarf2_per_cu_data);
memset (this_cu, 0, sizeof (*this_cu));
}
else
{
- auto sig_type = XOBNEW (&objfile->objfile_obstack,
+ auto sig_type = XOBNEW (&dwarf2_per_objfile->obstack,
struct signatured_type);
memset (sig_type, 0, sizeof (*sig_type));
sig_type->signature = cu_header.signature;
@@ -10100,7 +10090,8 @@ dw2_linkage_name (struct die_info *die, struct dwarf2_cu *cu)
For Ada, return the DIE's linkage name rather than the fully qualified
name. PHYSNAME is ignored..

- The result is allocated on the objfile_obstack and canonicalized. */
+ The result is allocated on the dwarf2_per_objfile obstack and
+ canonicalized. */

static const char *
dwarf2_compute_name (const char *name,
@@ -11255,7 +11246,8 @@ create_cus_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
if (cus_htab == NULL)
cus_htab = allocate_dwo_unit_table ();

- dwo_unit = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct dwo_unit);
+ dwo_unit = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack,
+ struct dwo_unit);
*dwo_unit = read_unit;
slot = htab_find_slot (cus_htab.get (), dwo_unit, INSERT);
gdb_assert (slot != NULL);
@@ -11458,7 +11450,7 @@ create_dwp_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
pulongest (nr_slots), dwp_file->name);
}

- htab = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct dwp_hash_table);
+ htab = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack, struct dwp_hash_table);
htab->version = version;
htab->nr_columns = nr_columns;
htab->nr_units = nr_units;
@@ -11655,7 +11647,6 @@ create_dwo_unit_in_dwp_v1 (struct dwarf2_per_objfile *dwarf2_per_objfile,
const char *comp_dir,
ULONGEST signature, int is_debug_types)
{
- struct objfile *objfile = dwarf2_per_objfile->objfile;
const struct dwp_hash_table *dwp_htab =
is_debug_types ? dwp_file->tus : dwp_file->cus;
bfd *dbfd = dwp_file->dbfd.get ();
@@ -11760,7 +11751,7 @@ create_dwo_unit_in_dwp_v1 (struct dwarf2_per_objfile *dwarf2_per_objfile,
virtual_dwo_name.c_str ());
}
dwo_file = new struct dwo_file;
- dwo_file->dwo_name = objfile->intern (virtual_dwo_name);
+ dwo_file->dwo_name = dwarf2_per_objfile->objfile->intern (virtual_dwo_name);
dwo_file->comp_dir = comp_dir;
dwo_file->sections.abbrev = sections.abbrev;
dwo_file->sections.line = sections.line;
@@ -11789,11 +11780,11 @@ create_dwo_unit_in_dwp_v1 (struct dwarf2_per_objfile *dwarf2_per_objfile,
dwo_file = (struct dwo_file *) *dwo_file_slot;
}

- dwo_unit = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct dwo_unit);
+ dwo_unit = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack, struct dwo_unit);
dwo_unit->dwo_file = dwo_file;
dwo_unit->signature = signature;
dwo_unit->section =
- XOBNEW (&objfile->objfile_obstack, struct dwarf2_section_info);
+ XOBNEW (&dwarf2_per_objfile->obstack, struct dwarf2_section_info);
*dwo_unit->section = sections.info_or_types;
/* dwo_unit->{offset,length,type_offset_in_tu} are set later. */

@@ -11854,7 +11845,6 @@ create_dwo_unit_in_dwp_v2 (struct dwarf2_per_objfile *dwarf2_per_objfile,
const char *comp_dir,
ULONGEST signature, int is_debug_types)
{
- struct objfile *objfile = dwarf2_per_objfile->objfile;
const struct dwp_hash_table *dwp_htab =
is_debug_types ? dwp_file->tus : dwp_file->cus;
bfd *dbfd = dwp_file->dbfd.get ();
@@ -11955,7 +11945,7 @@ create_dwo_unit_in_dwp_v2 (struct dwarf2_per_objfile *dwarf2_per_objfile,
virtual_dwo_name.c_str ());
}
dwo_file = new struct dwo_file;
- dwo_file->dwo_name = objfile->intern (virtual_dwo_name);
+ dwo_file->dwo_name = dwarf2_per_objfile->objfile->intern (virtual_dwo_name);
dwo_file->comp_dir = comp_dir;
dwo_file->sections.abbrev =
create_dwp_v2_section (dwarf2_per_objfile, &dwp_file->sections.abbrev,
@@ -11998,11 +11988,11 @@ create_dwo_unit_in_dwp_v2 (struct dwarf2_per_objfile *dwarf2_per_objfile,
dwo_file = (struct dwo_file *) *dwo_file_slot;
}

- dwo_unit = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct dwo_unit);
+ dwo_unit = OBSTACK_ZALLOC (&dwarf2_per_objfile->obstack, struct dwo_unit);
dwo_unit->dwo_file = dwo_file;
dwo_unit->signature = signature;
dwo_unit->section =
- XOBNEW (&objfile->objfile_obstack, struct dwarf2_section_info);
+ XOBNEW (&dwarf2_per_objfile->obstack, struct dwarf2_section_info);
*dwo_unit->section = create_dwp_v2_section (dwarf2_per_objfile,
is_debug_types
? &dwp_file->sections.types
@@ -12508,7 +12498,7 @@ open_and_init_dwp_file (struct dwarf2_per_objfile *dwarf2_per_objfile)

dwp_file->num_sections = elf_numsections (dwp_file->dbfd);
dwp_file->elf_sections =
- OBSTACK_CALLOC (&objfile->objfile_obstack,
+ OBSTACK_CALLOC (&dwarf2_per_objfile->obstack,
dwp_file->num_sections, asection *);

bfd_map_over_sections (dwp_file->dbfd.get (),
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index bd743acc715..8dbda90aa59 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -126,6 +126,11 @@ struct dwarf2_per_objfile
const dwarf2_debug_sections &names);

public:
+ /* Objects that can be shared across objfiles are stored in this
+ obstack or on the psymtab obstack, while objects that are
+ objfile-specific are stored on the objfile obstack. */
+ auto_obstack obstack;
+
dwarf2_section_info info {};
dwarf2_section_info abbrev {};
dwarf2_section_info line {};
--
2.26.2