[PATCH 03/14] Introduce dwarf2_per_objfile::obstack

Tom Tromey
2020-02-15T16:55:00Z

Currently much of the DWARF-related data is stored on the obfile
obstack. This prevents sharing this data across objfiles, so this
patch adds a new obstack to dwarf2_per_objfile.

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.

gdb/ChangeLog
2020-02-15 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, dw2_get_real_path)
(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.
---
gdb/ChangeLog | 17 +++++++++
gdb/dwarf2/read.c | 88 ++++++++++++++++++++++-------------------------
gdb/dwarf2/read.h | 5 +++
3 files changed, 64 insertions(+), 46 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 81d8cbf0b13..d3060be630d 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -2280,8 +2280,8 @@ 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. */
@@ -2412,9 +2412,8 @@ 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,
@@ -2422,16 +2421,15 @@ 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;
}
@@ -2516,7 +2514,7 @@ 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;
@@ -2525,7 +2523,7 @@ 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);
@@ -2573,7 +2571,7 @@ 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;
@@ -2582,7 +2580,7 @@ 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);
@@ -3094,7 +3092,6 @@ 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;
@@ -3143,7 +3140,7 @@ 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);
@@ -3157,7 +3154,8 @@ 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)
@@ -3202,8 +3200,12 @@ dw2_get_real_path (struct objfile *objfile,
struct quick_file_names *qfn, int index)
{
if (qfn->real_names == NULL)
- qfn->real_names = OBSTACK_CALLOC (&objfile->objfile_obstack,
- qfn->num_file_names, const char *);
+ {
+ struct dwarf2_per_objfile *dwarf2_per_objfile
+ = get_dwarf2_per_objfile (objfile);
+ qfn->real_names = OBSTACK_CALLOC (&dwarf2_per_objfile->obstack,
+ qfn->num_file_names, const char *);
+ }

if (qfn->real_names[index] == NULL)
qfn->real_names[index] = gdb_realpath (qfn->file_names[index]).release ();
@@ -5753,7 +5755,7 @@ 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);
}

@@ -5909,10 +5911,7 @@ dwarf2_create_include_psymtab (const char *name, dwarf2_psymtab *pst,
dwarf2_psymtab *subpst = new dwarf2_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;
@@ -6075,7 +6074,7 @@ 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;
@@ -6089,7 +6088,7 @@ 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;
@@ -6201,13 +6200,11 @@ 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);
@@ -6216,7 +6213,7 @@ 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);
}

@@ -7108,18 +7105,17 @@ 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
@@ -7837,13 +7833,13 @@ 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;
@@ -9985,7 +9981,8 @@ 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,
@@ -11145,7 +11142,8 @@ create_cus_hash_table (struct dwarf2_per_objfile *dwarf2_per_objfile,
if (cus_htab == NULL)
cus_htab = allocate_dwo_unit_table (objfile);

- 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);
@@ -11348,7 +11346,7 @@ 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;
@@ -11545,7 +11543,6 @@ 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 ();
@@ -11650,7 +11647,7 @@ 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 = obstack_strdup (&objfile->objfile_obstack,
+ dwo_file->dwo_name = obstack_strdup (&dwarf2_per_objfile->obstack,
virtual_dwo_name);
dwo_file->comp_dir = comp_dir;
dwo_file->sections.abbrev = sections.abbrev;
@@ -11680,11 +11677,11 @@ 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. */

@@ -11745,7 +11742,6 @@ 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 ();
@@ -11846,7 +11842,7 @@ 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 = obstack_strdup (&objfile->objfile_obstack,
+ dwo_file->dwo_name = obstack_strdup (&dwarf2_per_objfile->obstack,
virtual_dwo_name);
dwo_file->comp_dir = comp_dir;
dwo_file->sections.abbrev =
@@ -11890,11 +11886,11 @@ 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
@@ -12395,7 +12391,7 @@ 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 b06c2e218c1..a7ac3b6b025 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -118,6 +118,11 @@ private:
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 {};
--
2.17.2