The patch titled
Subject: x86: s/READ_ONCE_NOCHECK/READ_ONCE/ in arch_atomic[64]_read()
has been added to the -mm tree. Its filename is
asm-generic-x86-wrap-atomic-operations-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/asm-generic-x86-wrap-atomic-operations-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/asm-generic-x86-wrap-atomic-operations-fix.patch
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------------------------------------------------------
From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Subject: x86: s/READ_ONCE_NOCHECK/READ_ONCE/ in arch_atomic[64]_read()
Two problems was reported with READ_ONCE_NOCHECK in arch_atomic_read:
1. Andrey Ryabinin reported significant binary size increase
(+400K of text). READ_ONCE_NOCHECK is intentionally compiled to
non-inlined function call, and I counted 640 copies of it in my vmlinux.
2. Arnd Bergmann reported a new splat of too large frame sizes.
A single inlined KASAN check is very cheap, a non-inlined function
call with KASAN/KCOV instrumentation can easily be more expensive.
Switch to READ_ONCE() in arch_atomic[64]_read().
Link: http://lkml.kernel.org/r/20170322125740.85337-1-dvyukov@xxxxxxxxxx
Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Reported-by: Arnd Bergmann <arnd@xxxxxxxx>
Reported-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/atomic.h | 15 ++++++---------
arch/x86/include/asm/atomic64_64.h | 2 +-
2 files changed, 7 insertions(+), 10 deletions(-)
diff -puN arch/x86/include/asm/atomic.h~asm-generic-x86-wrap-atomic-operations-fix arch/x86/include/asm/atomic.h
--- a/arch/x86/include/asm/atomic.h~asm-generic-x86-wrap-atomic-operations-fix
+++ a/arch/x86/include/asm/atomic.h
@@ -24,10 +24,13 @@
static __always_inline int arch_atomic_read(const atomic_t *v)
{
/*
- * We use READ_ONCE_NOCHECK() because atomic_read() contains KASAN
- * instrumentation. Double instrumentation is unnecessary.
+ * Note: READ_ONCE() here leads to double instrumentation as
+ * both READ_ONCE() and atomic_read() contain instrumentation.
+ * This is deliberate choice. READ_ONCE_NOCHECK() is compiled to a
+ * non-inlined function call that considerably increases binary size
+ * and stack usage under KASAN.
*/
- return READ_ONCE_NOCHECK((v)->counter);
+ return READ_ONCE((v)->counter);
}
/**
@@ -39,12 +42,6 @@ static __always_inline int arch_atomic_r
*/
static __always_inline void arch_atomic_set(atomic_t *v, int i)
{
- /*
- * We could use WRITE_ONCE_NOCHECK() if it exists, similar to
- * READ_ONCE_NOCHECK() in arch_atomic_read(). But there is no such
- * thing at the moment, and introducing it for this case does not
- * worth it.
- */
WRITE_ONCE(v->counter, i);
}
diff -puN arch/x86/include/asm/atomic64_64.h~asm-generic-x86-wrap-atomic-operations-fix arch/x86/include/asm/atomic64_64.h
--- a/arch/x86/include/asm/atomic64_64.h~asm-generic-x86-wrap-atomic-operations-fix
+++ a/arch/x86/include/asm/atomic64_64.h
@@ -18,7 +18,7 @@
*/
static inline long arch_atomic64_read(const atomic64_t *v)
{
- return READ_ONCE_NOCHECK((v)->counter);
+ return READ_ONCE((v)->counter);
}
/**
_
Patches currently in -mm which might be from dvyukov@xxxxxxxxxx are
fault-inject-support-systematic-fault-injection.patch
kasan-allow-kasan_check_read-write-to-accept-pointers-to-volatiles.patch
asm-generic-x86-wrap-atomic-operations.patch
asm-generic-x86-wrap-atomic-operations-fix.patch
asm-generic-add-kasan-instrumentation-to-atomic-operations.patch
asm-generic-fix-compilation-failure-in-cmpxchg_double.patch
x86-remove-unused-atomic_inc_short.patch
x86-asm-generic-add-kasan-instrumentation-to-bitops.patch
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