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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: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon 2019-12-19 17:11:43 +00:00
parent 549887271a
commit 10223c5286
1 changed files with 8 additions and 8 deletions
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16
arch/arm64/include/asm/barrier.h
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@ -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>