[PATCH v4 3/6] perf libdw: Fix libdw API contract violations

Ian Rogers
2026-05-03T17:10:50Z

Check return values of `dwfl_report_end` and `dwfl_module_addrdie`.
Check `die_get_call_lineno` for errors.

Additionally:
- Introduce `inline_node__clear_frames()` to clean up partial
allocations.
- Ensure `*file` is freed and inline frames are cleared on error in
`libdw__addr2line()` to prevent memory leaks and duplicated
callchains when falling back to other unwinders.
- Allow DWARF line 0 in `libdw_a2l_cb()`, as it is a valid
reference for compiler-generated code.
- Fix the parent srcline lookup in `libdw_a2l_cb()` to target the
correct parent node depending on the callchain order
(ORDER_CALLER/ORDER_CALLEE).

Fixes: b7a2b011e962 ("perf powerpc: Unify the skip-callchain-idx libdw with that for addr2line")
Fixes: 88c51002d06f ("perf addr2line: Add a libdw implementation")
Assisted-by: Gemini-CLI:Google Gemini 3
Signed-off-by: Ian Rogers <irogers@google.com>
---
v4:
- Fix memory leaks and duplicated callchains on unwinding errors.
- Support DWARF line 0 in inline list.
- Fix callchain parent update in ORDER_CALLER mode.
---
tools/perf/util/libdw.c | 84 +++++++++++++++++++++++++++++++--------
tools/perf/util/srcline.c | 9 ++++-
tools/perf/util/srcline.h | 1 +
3 files changed, 77 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/libdw.c b/tools/perf/util/libdw.c
index 216977884103..e69ff4cea856 100644
--- a/tools/perf/util/libdw.c
+++ b/tools/perf/util/libdw.c
@@ -4,6 +4,7 @@
#include "srcline.h"
#include "symbol.h"
#include "dwarf-aux.h"
+#include "callchain.h"
#include <fcntl.h>
#include <unistd.h>
#include <elfutils/libdwfl.h>
@@ -60,7 +61,11 @@ struct Dwfl *dso__libdw_dwfl(struct dso *dso)
return NULL;
}

- dwfl_report_end(dwfl, /*removed=*/NULL, /*arg=*/NULL);
+ if (dwfl_report_end(dwfl, NULL, NULL) != 0) {
+ dwfl_end(dwfl);
+ return NULL;
+ }
+
dso__set_libdw(dso, dwfl);

return dwfl;
@@ -72,41 +77,70 @@ struct libdw_a2l_cb_args {
struct inline_node *node;
char *leaf_srcline;
bool leaf_srcline_used;
+ int err;
};

static int libdw_a2l_cb(Dwarf_Die *die, void *_args)
{
struct libdw_a2l_cb_args *args = _args;
- struct symbol *inline_sym = new_inline_sym(args->dso, args->sym, dwarf_diename(die));
+ const char *name = dwarf_diename(die);
+ struct symbol *inline_sym = new_inline_sym(args->dso, args->sym, name ?: "unknown");
const char *call_fname = die_get_call_file(die);
+ int call_lineno = die_get_call_lineno(die);
char *call_srcline = srcline__unknown;
- struct inline_list *ilist;

- if (!inline_sym)
- return -ENOMEM;
+ if (!inline_sym) {
+ args->err = -ENOMEM;
+ return DWARF_CB_ABORT;
+ }

/* Assign caller information to the parent. */
- if (call_fname)
- call_srcline = srcline_from_fileline(call_fname, die_get_call_lineno(die));
+ if (call_fname && call_lineno >= 0)
+ call_srcline = srcline_from_fileline(call_fname, call_lineno);

- list_for_each_entry(ilist, &args->node->val, list) {
- if (args->leaf_srcline == ilist->srcline)
+ if (!list_empty(&args->node->val)) {
+ struct inline_list *parent;
+
+ if (callchain_param.order == ORDER_CALLEE)
+ parent = list_first_entry(&args->node->val, struct inline_list, list);
+ else
+ parent = list_last_entry(&args->node->val, struct inline_list, list);
+
+ if (args->leaf_srcline == parent->srcline)
args->leaf_srcline_used = false;
- else if (ilist->srcline != srcline__unknown)
- free(ilist->srcline);
- ilist->srcline = call_srcline;
+ else if (parent->srcline != srcline__unknown)
+ free(parent->srcline);
+ parent->srcline = call_srcline;
call_srcline = NULL;
- break;
}
if (call_srcline && call_srcline != srcline__unknown)
free(call_srcline);

/* Add this symbol to the chain as the leaf. */
if (!args->leaf_srcline_used) {
- inline_list__append_tail(inline_sym, args->leaf_srcline, args->node);
+ if (inline_list__append_tail(inline_sym, args->leaf_srcline, args->node) != 0) {
+ args->err = -ENOMEM;
+ if (inline_sym->inlined)
+ symbol__delete(inline_sym);
+ return DWARF_CB_ABORT;
+ }
args->leaf_srcline_used = true;
} else {
- inline_list__append_tail(inline_sym, strdup(args->leaf_srcline), args->node);
+ char *srcline = strdup(args->leaf_srcline);
+
+ if (!srcline) {
+ args->err = -ENOMEM;
+ if (inline_sym->inlined)
+ symbol__delete(inline_sym);
+ return DWARF_CB_ABORT;
+ }
+ if (inline_list__append_tail(inline_sym, srcline, args->node) != 0) {
+ free(srcline);
+ args->err = -ENOMEM;
+ if (inline_sym->inlined)
+ symbol__delete(inline_sym);
+ return DWARF_CB_ABORT;
+ }
}
return 0;
}
@@ -162,11 +196,29 @@ int libdw__addr2line(u64 addr, char **file, unsigned int *line_nr,
.leaf_srcline = srcline_from_fileline(src ?: "<unknown>", lineno),
};

+ if (!args.leaf_srcline) {
+ if (file && *file) {
+ free(*file);
+ *file = NULL;
+ }
+ return 0;
+ }
+
/* Walk from the parent down to the leaf. */
- cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);
+ if (cudie)
+ cu_walk_functions_at(cudie, addr, libdw_a2l_cb, &args);

if (!args.leaf_srcline_used)
free(args.leaf_srcline);
+
+ if (args.err) {
+ if (file && *file) {
+ free(*file);
+ *file = NULL;
+ }
+ inline_node__clear_frames(node);
+ return 0;
+ }
}
return 1;
}
diff --git a/tools/perf/util/srcline.c b/tools/perf/util/srcline.c
index db164d258163..62884428fb5a 100644
--- a/tools/perf/util/srcline.c
+++ b/tools/perf/util/srcline.c
@@ -429,10 +429,13 @@ struct inline_node *dso__parse_addr_inlines(struct dso *dso, u64 addr,
return addr2inlines(dso_name, addr, dso, sym);
}

-void inline_node__delete(struct inline_node *node)
+void inline_node__clear_frames(struct inline_node *node)
{
struct inline_list *ilist, *tmp;

+ if (node == NULL)
+ return;
+
list_for_each_entry_safe(ilist, tmp, &node->val, list) {
list_del_init(&ilist->list);
zfree_srcline(&ilist->srcline);
@@ -441,7 +444,11 @@ void inline_node__delete(struct inline_node *node)
symbol__delete(ilist->symbol);
free(ilist);
}
+}

+void inline_node__delete(struct inline_node *node)
+{
+ inline_node__clear_frames(node);
free(node);
}

diff --git a/tools/perf/util/srcline.h b/tools/perf/util/srcline.h
index 7c37b3bf9ce7..1018cbc886d6 100644
--- a/tools/perf/util/srcline.h
+++ b/tools/perf/util/srcline.h
@@ -47,6 +47,7 @@ struct inline_node *dso__parse_addr_inlines(struct dso *dso, u64 addr,
struct symbol *sym);
/* free resources associated to the inline node list */
void inline_node__delete(struct inline_node *node);
+void inline_node__clear_frames(struct inline_node *node);

/* insert the inline node list into the DSO, which will take ownership */
void inlines__tree_insert(struct rb_root_cached *tree,
--
2.54.0.545.g6539524ca2-goog