[PATCH RFC 4/9] mm/kmemleak: print trie-backed stack depot traces

[Caleb Kan <calebkan1106@gmail.com>]

From: Caleb Kan <ckan@cloudflare.com>

kmemleak stores allocation backtraces as persistent stack depot handles.
When trie storage is enabled, stack_depot_fetch() cannot return a pointer
to contiguous stack-record entries, so leak reports would omit the saved
backtrace.

Use stack_depot_fetch_into() with a MAX_TRACE-sized local array before
formatting the report. MAX_TRACE matches the save-side limit, so every
valid kmemleak trace fits without truncation. Preserve frame order and the
existing report format for hash-backed handles.

Signed-off-by: Caleb Kan <ckan@cloudflare.com>
---
 mm/kmemleak.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 8fa409a4f9fb..c42741a88bd4 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -378,10 +378,10 @@ static void __print_unreferenced(struct seq_file *seq,
 				 bool hex_dump)
 {
 	int i;
-	unsigned long *entries;
+	unsigned long entries[MAX_TRACE];
 	unsigned int nr_entries;
 
-	nr_entries = stack_depot_fetch(object->trace_handle, &entries);
+	nr_entries = stack_depot_fetch_into(object->trace_handle, entries, ARRAY_SIZE(entries));
 	warn_or_seq_printf(seq, "unreferenced object%s 0x%08lx (size %zu):\n",
 			   __object_type_str(object),
 			   object->pointer, object->size);

-- 
Git-155)