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cleanup: Annotate guard constructors with nonnull

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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
This commit is contained in:
Dmitry Ilvokhin 2026-06-02 07:12:52 +00:00 committed by Peter Zijlstra
parent 08d4a7837f
commit 22302af28d
2 changed files with 12 additions and 1 deletions
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4
include/linux/cleanup.h
View File

@ -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; \

9
include/linux/compiler_attributes.h
View File

@ -230,6 +230,15 @@
*/
#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