linux-kernel - [PATCHv3 02/12] atomics/x86: reduce arch

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Message-Id: <20180705164053.10073-3-mark.rutland@arm.com>
Date:   Thu,  5 Jul 2018 17:40:43 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        peterz@...radead.org, will.deacon@....com
Cc:     andy.shevchenko@...il.com, arnd@...db.de, aryabinin@...tuozzo.com,
        boqun.feng@...il.com, catalin.marinas@....com, dvyukov@...gle.com,
        glider@...gle.com, hpa@...or.com, linuxdrivers@...otech.com,
        mark.rutland@....com, mingo@...nel.org, mingo@...hat.com,
        parri.andrea@...il.com, peter@...leysoftware.com,
        tglx@...utronix.de
Subject: [PATCHv3 02/12] atomics/x86: reduce arch_cmpxchg64*() instrumentation

Currently x86's arch_cmpxchg64() and arch_cmpxchg64_local() are
instrumented twice, as they call into instrumented atomics rather than
their arch_ equivalents.

A call to cmpxchg64() results in:

  cmpxchg64()
    kasan_check_write()
    arch_cmpxchg64()
      cmpxchg()
        kasan_check_write()
        arch_cmpxchg()

Let's fix this up and call the arch_ equivalents, resulting in:

  cmpxchg64()
    kasan_check_write()
    arch_cmpxchg64()
      arch_cmpxchg()

Signed-off-by: Mark Rutland <mark.rutland@....com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Will Deacon <will.deacon@....com>
---
 arch/x86/include/asm/cmpxchg_64.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index bfca3b346c74..072e5459fe2f 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -10,13 +10,13 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
 #define arch_cmpxchg64(ptr, o, n)					\
 ({									\
 	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
-	cmpxchg((ptr), (o), (n));					\
+	arch_cmpxchg((ptr), (o), (n));					\
 })
 
 #define arch_cmpxchg64_local(ptr, o, n)					\
 ({									\
 	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
-	cmpxchg_local((ptr), (o), (n));					\
+	arch_cmpxchg_local((ptr), (o), (n));				\
 })
 
 #define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16)
-- 
2.11.0