The following commit has been merged into the locking/core branch of tip:

Commit-ID:     22302af28d3f7c3ca38536978c80db51d2a9e283
Gitweb:        https://git.kernel.org/tip/22302af28d3f7c3ca38536978c80db51d2a9e283
Author:        Dmitry Ilvokhin <d@ilvokhin.com>
AuthorDate:    Tue, 02 Jun 2026 07:12:52 
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 03 Jun 2026 11:38:48 +02:00

cleanup: Annotate guard constructors with nonnull

Add __nonnull_args() to unconditional guard constructors so the compiler
warns when NULL is statically known to be passed:

- DEFINE_GUARD(): re-declare the constructor with __nonnull_args().
- __DEFINE_LOCK_GUARD_1(): annotate the constructor directly.

DEFINE_LOCK_GUARD_0() needs no annotation: its constructor takes no
pointer arguments (.lock is hardcoded to (void *)1).

Define the __nonnull_args() macro in compiler_attributes.h, following
the existing convention for attribute wrappers. Deliberately not named
'__nonnull', to avoid clashing with glibc's __nonnull() when kernel and
userspace headers are combined (User Mode Linux for example).

Signed-off-by: Dmitry Ilvokhin <d@ilvokhin.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/85fee12eec20abfcf711443518e8f0caec982a86.1780064327.git.d@ilvokhin.com
---
 include/linux/cleanup.h             |  4 +++-
 include/linux/compiler_attributes.h |  9 +++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index ea95ca4..4e60d51 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -397,6 +397,7 @@ static __maybe_unused const bool class_##_name##_is_conditional = _is_cond
 	__DEFINE_GUARD_LOCK_PTR(_name, _T)
 
 #define DEFINE_GUARD(_name, _type, _lock, _unlock) \
+	static __always_inline __nonnull_args() _type class_##_name##_constructor(_type _T); \
 	DEFINE_CLASS(_name, _type, if (_T) { _unlock; }, ({ _lock; _T; }), _type _T); \
 	DEFINE_CLASS_IS_GUARD(_name)
 
@@ -497,7 +498,8 @@ static __always_inline void class_##_name##_destructor(class_##_name##_t *_T) \
 __DEFINE_GUARD_LOCK_PTR(_name, &_T->lock)
 
 #define __DEFINE_LOCK_GUARD_1(_name, _type, ...)			\
-static __always_inline class_##_name##_t class_##_name##_constructor(_type *l) \
+static __always_inline __nonnull_args()					\
+class_##_name##_t class_##_name##_constructor(_type *l)			\
 	__no_context_analysis						\
 {									\
 	class_##_name##_t _t = { .lock = l }, *_T = &_t;		\
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index c16d419..cffe093 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -231,6 +231,15 @@
 #define   noinline                      __attribute__((__noinline__))
 
 /*
+ * Note: deliberately not named '__nonnull', to avoid clashing with glibc's
+ * __nonnull() when kernel and userspace headers are combined.
+ *
+ *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-nonnull
+ * clang: https://clang.llvm.org/docs/AttributeReference.html#nonnull
+ */
+#define __nonnull_args(x...)		__attribute__((__nonnull__(x)))
+
+/*
  * Optional: only supported since gcc >= 8
  * Optional: not supported by clang
  *