[PATCH 5/6] kasan: generic: introduce kasan_record_aux_stack_noalloc()

[Marco Elver <elver@google.com>]

Introduce a variant of kasan_record_aux_stack() that does not do any
memory allocation through stackdepot. This will permit using it in
contexts that cannot allocate any memory.

Signed-off-by: Marco Elver <elver@google.com>
---
 include/linux/kasan.h |  2 ++
 mm/kasan/generic.c    | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index dd874a1ee862..736d7b458996 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -370,12 +370,14 @@ static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
 void kasan_cache_shrink(struct kmem_cache *cache);
 void kasan_cache_shutdown(struct kmem_cache *cache);
 void kasan_record_aux_stack(void *ptr);
+void kasan_record_aux_stack_noalloc(void *ptr);
 
 #else /* CONFIG_KASAN_GENERIC */
 
 static inline void kasan_cache_shrink(struct kmem_cache *cache) {}
 static inline void kasan_cache_shutdown(struct kmem_cache *cache) {}
 static inline void kasan_record_aux_stack(void *ptr) {}
+static inline void kasan_record_aux_stack_noalloc(void *ptr) {}
 
 #endif /* CONFIG_KASAN_GENERIC */
 
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 2a8e59e6326d..84a038b07c6f 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -328,7 +328,7 @@ DEFINE_ASAN_SET_SHADOW(f3);
 DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
 
-void kasan_record_aux_stack(void *addr)
+static void __kasan_record_aux_stack(void *addr, bool can_alloc)
 {
 	struct page *page = kasan_addr_to_page(addr);
 	struct kmem_cache *cache;
@@ -345,7 +345,17 @@ void kasan_record_aux_stack(void *addr)
 		return;
 
 	alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
-	alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT, true);
+	alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT, can_alloc);
+}
+
+void kasan_record_aux_stack(void *addr)
+{
+	return __kasan_record_aux_stack(addr, true);
+}
+
+void kasan_record_aux_stack_noalloc(void *addr)
+{
+	return __kasan_record_aux_stack(addr, false);
 }
 
 void kasan_set_free_info(struct kmem_cache *cache,
-- 
2.33.0.153.gba50c8fa24-goog