[PATCH v4 5/6] perf annotate-data: Fix libdw API contract violations

Ian Rogers
2026-05-03T17:10:53Z

Check return values of `dwarf_aggregate_size` and `dwarf_formudata`.

Additionally:
- Avoid `vfprintf` undefined behavior with `NULL` strings by using
the `die_name()` helper for `dwarf_diename()` in `pr_*` calls.
- Use `die_get_data_member_location()` (updated to use
`dwarf_attr_integrate`) to correctly parse location expressions
for inherited member locations in the fallback path when
`dwarf_formudata()` fails.

Fixes: 2bc3cf575a16 ("perf annotate-data: Improve debug message with location info")
Fixes: 4a111cadac85 ("perf annotate-data: Add member field in the data type")
Fixes: 8b1042c425f6 ("perf annotate-data: Set bitfield member offset and size properly")
Fixes: fc044c53b99f ("perf annotate-data: Add dso->data_types tree")
Assisted-by: Gemini-CLI:Google Gemini 3
Signed-off-by: Ian Rogers <irogers@google.com>
---
v4:
- Safe DWARF name printing in annotate-data.
- Fix fallback location expression parsing for inherited data members.
---
tools/perf/util/annotate-data.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 1eff0a27237d..2eacbba51f32 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -74,7 +74,8 @@ void pr_debug_type_name(Dwarf_Die *die, enum type_state_kind kind)
break;
}

- dwarf_aggregate_size(die, &size);
+ if (dwarf_aggregate_size(die, &size) != 0)
+ size = 0;

strbuf_init(&sb, 32);
die_get_typename_from_type(die, &sb);
@@ -146,9 +147,9 @@ static void pr_debug_scope(Dwarf_Die *scope_die)

tag = dwarf_tag(scope_die);
if (tag == DW_TAG_subprogram)
- pr_info("[function] %s\n", dwarf_diename(scope_die));
+ pr_info("[function] %s\n", die_name(scope_die));
else if (tag == DW_TAG_inlined_subroutine)
- pr_info("[inlined] %s\n", dwarf_diename(scope_die));
+ pr_info("[inlined] %s\n", die_name(scope_die));
else if (tag == DW_TAG_lexical_block)
pr_info("[block]\n");
else
@@ -250,9 +251,12 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
if (dwarf_aggregate_size(&die_mem, &size) < 0)
size = 0;

- if (dwarf_attr_integrate(die, DW_AT_data_member_location, &attr))
- dwarf_formudata(&attr, &loc);
- else {
+ if (dwarf_attr_integrate(die, DW_AT_data_member_location, &attr)) {
+ if (dwarf_formudata(&attr, &loc) != 0) {
+ if (die_get_data_member_location(die, &loc) != 0)
+ loc = 0;
+ }
+ } else {
/* bitfield member */
if (dwarf_attr_integrate(die, DW_AT_data_bit_offset, &attr) &&
dwarf_formudata(&attr, &loc) == 0)
@@ -273,7 +277,9 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
dwarf_diename(die), (long)bit_size) < 0)
member->var_name = NULL;
} else {
- member->var_name = strdup(dwarf_diename(die));
+ const char *name = dwarf_diename(die);
+
+ member->var_name = strdup(name);
}

if (member->var_name == NULL) {
@@ -370,7 +376,8 @@ static struct annotated_data_type *dso__findnew_data_type(struct dso *dso,
if (dwarf_tag(type_die) == DW_TAG_typedef)
die_get_real_type(type_die, type_die);

- dwarf_aggregate_size(type_die, &size);
+ if (dwarf_aggregate_size(type_die, &size) != 0)
+ size = 0;

/* Check existing nodes in dso->data_types tree */
key.self.type_name = type_name;
@@ -1569,7 +1576,7 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die)
offset = loc->offset;

pr_debug_dtp("CU for %s (die:%#lx)\n",
- dwarf_diename(&cu_die), (long)dwarf_dieoffset(&cu_die));
+ die_name(&cu_die), (long)dwarf_dieoffset(&cu_die));

if (reg == DWARF_REG_PC) {
if (get_global_var_type(&cu_die, dloc, dloc->ip, dloc->var_addr,
@@ -1636,7 +1643,7 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die)
}

pr_debug_dtp("found \"%s\" (die: %#lx) in scope=%d/%d (die: %#lx) ",
- dwarf_diename(&var_die), (long)dwarf_dieoffset(&var_die),
+ die_name(&var_die), (long)dwarf_dieoffset(&var_die),
i+1, nr_scopes, (long)dwarf_dieoffset(&scopes[i]));

if (reg == DWARF_REG_PC) {
--
2.54.0.545.g6539524ca2-goog