Commit 10223c52 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros 



Passing volatile-qualified pointers to the arm64 implementations of the
load-acquire/store-release macros results in a re-load from the stack
and a bunch of associated stack-protector churn due to the temporary
result variable inheriting the volatile semantics thanks to the use of
'typeof()'.

Define these temporary variables using 'unqual_scalar_typeof' to drop
the volatile qualifier in the case that they are scalar types.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 54988727

arch/arm64/include/asm/barrier.h

+8 −8
Original line number Diff line number Diff line
@@ -76,8 +76,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long idx, 
#define __smp_store_release(p, v)					\

do {									\

	typeof(p) __p = (p);						\

	union { typeof(*p) __val; char __c[1]; } __u =			\

		{ .__val = (__force typeof(*p)) (v) };			\

	union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u =	\

		{ .__val = (__force __unqual_scalar_typeof(*p)) (v) };	\

	compiletime_assert_atomic_type(*p);				\

	kasan_check_write(__p, sizeof(*p));				\

	switch (sizeof(*p)) {						\
@@ -110,7 +110,7 @@ do { \ 


#define __smp_load_acquire(p)						\

({									\

	union { typeof(*p) __val; char __c[1]; } __u;			\

	union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u;	\

	typeof(p) __p = (p);						\

	compiletime_assert_atomic_type(*p);				\

	kasan_check_read(__p, sizeof(*p));				\
@@ -136,33 +136,33 @@ do { \ 
			: "Q" (*__p) : "memory");			\

		break;							\

	}								\

	__u.__val;							\

	(typeof(*p))__u.__val;						\

})



#define smp_cond_load_relaxed(ptr, cond_expr)				\

({									\

	typeof(ptr) __PTR = (ptr);					\

	typeof(*ptr) VAL;						\

	__unqual_scalar_typeof(*ptr) VAL;				\

	for (;;) {							\

		VAL = READ_ONCE(*__PTR);				\

		if (cond_expr)						\

			break;						\

		__cmpwait_relaxed(__PTR, VAL);				\

	}								\

	VAL;								\

	(typeof(*ptr))VAL;						\

})



#define smp_cond_load_acquire(ptr, cond_expr)				\

({									\

	typeof(ptr) __PTR = (ptr);					\

	typeof(*ptr) VAL;						\

	__unqual_scalar_typeof(*ptr) VAL;				\

	for (;;) {							\

		VAL = smp_load_acquire(__PTR);				\

		if (cond_expr)						\

			break;						\

		__cmpwait_relaxed(__PTR, VAL);				\

	}								\

	VAL;								\

	(typeof(*ptr))VAL;						\

})



#include <asm-generic/barrier.h>

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