From: Dmitry Vyukov <dvyukov@google.com>
To: mark.rutland@arm.com, peterz@infradead.org, mingo@redhat.com,
will.deacon@arm.com, hpa@zytor.com, aryabinin@virtuozzo.com,
kasan-dev@googlegroups.com, x86@kernel.org,
linux-kernel@vger.kernel.org, tglx@linutronix.de
Cc: Dmitry Vyukov <dvyukov@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org
Subject: [PATCH v6 4/4] asm-generic, x86: add comments for atomic instrumentation
Date: Mon, 29 Jan 2018 18:26:07 +0100 [thread overview]
Message-ID: <cc595efc644bb905407012d82d3eb8bac3368e7a.1517246437.git.dvyukov@google.com> (raw)
In-Reply-To: <cover.1517246437.git.dvyukov@google.com>
In-Reply-To: <cover.1517246437.git.dvyukov@google.com>
The comments are factored out from the code changes to make them
easier to read. Add them separately to explain some non-obvious
aspects.
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Cc: x86@kernel.org
---
Changes since v3:
- rephrase comment in arch_atomic_read()
Changes since v5:
- remove comment explaining cmpxchg macro mess,
since we don't have the mess now.
---
arch/x86/include/asm/atomic.h | 4 ++++
include/asm-generic/atomic-instrumented.h | 21 +++++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 33afc966d6a9..0db6bec95489 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -24,6 +24,10 @@
*/
static __always_inline int arch_atomic_read(const atomic_t *v)
{
+ /*
+ * Note for KASAN: we deliberately don't use READ_ONCE_NOCHECK() here,
+ * it's non-inlined function that increases binary size and stack usage.
+ */
return READ_ONCE((v)->counter);
}
diff --git a/include/asm-generic/atomic-instrumented.h b/include/asm-generic/atomic-instrumented.h
index 82e080505982..ec07f23678ea 100644
--- a/include/asm-generic/atomic-instrumented.h
+++ b/include/asm-generic/atomic-instrumented.h
@@ -1,3 +1,15 @@
+/*
+ * This file provides wrappers with KASAN instrumentation for atomic operations.
+ * To use this functionality an arch's atomic.h file needs to define all
+ * atomic operations with arch_ prefix (e.g. arch_atomic_read()) and include
+ * this file at the end. This file provides atomic_read() that forwards to
+ * arch_atomic_read() for actual atomic operation.
+ * Note: if an arch atomic operation is implemented by means of other atomic
+ * operations (e.g. atomic_read()/atomic_cmpxchg() loop), then it needs to use
+ * arch_ variants (i.e. arch_atomic_read()/arch_atomic_cmpxchg()) to avoid
+ * double instrumentation.
+ */
+
#ifndef _LINUX_ATOMIC_INSTRUMENTED_H
#define _LINUX_ATOMIC_INSTRUMENTED_H
@@ -442,6 +454,15 @@ cmpxchg64_local_size(volatile u64 *ptr, u64 old, u64 new)
(u64)(new))); \
})
+/*
+ * Originally we had the following code here:
+ * __typeof__(p1) ____p1 = (p1);
+ * kasan_check_write(____p1, 2 * sizeof(*____p1));
+ * arch_cmpxchg_double(____p1, (p2), (o1), (o2), (n1), (n2));
+ * But it leads to compilation failures (see gcc issue 72873).
+ * So for now it's left non-instrumented.
+ * There are few callers of cmpxchg_double(), so it's not critical.
+ */
#define cmpxchg_double(p1, p2, o1, o2, n1, n2) \
({ \
arch_cmpxchg_double((p1), (p2), (o1), (o2), (n1), (n2)); \
--
2.16.0.rc1.238.g530d649a79-goog
next prev parent reply other threads:[~2018-01-29 17:30 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 17:26 [PATCH v6 0/4] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov
2018-01-29 17:26 ` [PATCH v6 1/4] locking/atomic: Add asm-generic/atomic-instrumented.h Dmitry Vyukov
2018-01-29 17:26 ` [PATCH v6 2/4] x86: switch atomic.h to use atomic-instrumented.h Dmitry Vyukov
2018-03-12 12:24 ` [tip:locking/core] locking/atomic/x86: Switch " tip-bot for Dmitry Vyukov
2018-01-29 17:26 ` [PATCH v6 3/4] asm-generic: add KASAN instrumentation to atomic operations Dmitry Vyukov
2018-03-12 12:24 ` [tip:locking/core] locking/atomic, asm-generic: Add " tip-bot for Dmitry Vyukov
2018-01-29 17:26 ` Dmitry Vyukov [this message]
2018-03-12 12:25 ` [tip:locking/core] locking/atomic, asm-generic, x86: Add comments for atomic instrumentation tip-bot for Dmitry Vyukov
2018-01-30 9:23 ` [PATCH v6 0/4] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov
2018-01-30 9:27 ` Dmitry Vyukov
2018-01-30 15:36 ` Will Deacon
2018-01-31 7:28 ` Ingo Molnar
2018-01-31 8:53 ` Dmitry Vyukov
2018-01-31 16:17 ` Will Deacon
2018-02-07 14:17 ` Dmitry Vyukov
2018-02-20 10:40 ` Dmitry Vyukov
2018-02-26 12:52 ` Dmitry Vyukov
-- strict thread matches above, loose matches on Subject: below --
2017-06-17 9:15 [PATCH v4 0/7] " Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 1/7] x86: un-macro-ify atomic ops implementation Dmitry Vyukov
2017-06-22 11:04 ` [tip:locking/core] locking/atomic/x86: Un-macro-ify " tip-bot for Dmitry Vyukov
2017-07-25 13:54 ` tip-bot for Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 2/7] x86: use s64* for old arg of atomic64_try_cmpxchg() Dmitry Vyukov
2017-06-22 11:04 ` [tip:locking/core] locking/atomic/x86: Use 's64 *' for 'old' argument " tip-bot for Dmitry Vyukov
2017-07-25 13:55 ` tip-bot for Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 3/7] asm-generic: add atomic-instrumented.h Dmitry Vyukov
2017-06-19 10:50 ` Mark Rutland
2017-06-22 11:05 ` [tip:locking/core] locking/atomic: Add asm-generic/atomic-instrumented.h tip-bot for Dmitry Vyukov
2018-03-12 12:23 ` [tip:locking/core] locking/atomic, asm-generic: " tip-bot for Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 4/7] x86: switch atomic.h to use atomic-instrumented.h Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 5/7] kasan: allow kasan_check_read/write() to accept pointers to volatiles Dmitry Vyukov
2017-06-19 10:50 ` Mark Rutland
2017-06-19 13:11 ` Dmitry Vyukov
2017-06-22 8:25 ` Ingo Molnar
2017-06-22 14:15 ` Dmitry Vyukov
2017-06-17 9:15 ` [PATCH v4 6/7] asm-generic: add KASAN instrumentation to atomic operations Dmitry Vyukov
2017-06-19 10:51 ` Mark Rutland
2017-06-17 9:15 ` [PATCH v4 7/7] asm-generic, x86: add comments for atomic instrumentation Dmitry Vyukov
2017-06-19 10:54 ` Mark Rutland
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