From: Andrew Morton <akpm@linux-foundation.org>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Michal Marek <mmarek@suse.cz>,
"long.wanglong" <long.wanglong@huawei.com>,
Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>
Subject: Re: [PATCH] kasan: use IS_ALIGNED in memory_is_poisoned_8()
Date: Fri, 11 Sep 2015 15:47:30 -0700 [thread overview]
Message-ID: <20150911154730.3a2151a0b111fed01acdaaa1@linux-foundation.org> (raw)
In-Reply-To: <55F23635.1010109@huawei.com>
On Fri, 11 Sep 2015 10:02:29 +0800 Xishi Qiu <qiuxishi@huawei.com> wrote:
> Use IS_ALIGNED() to determine whether the shadow span two bytes.
> It generates less code and more readable.
>
Please cc Andrey Ryabinin on kasan patches.
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -120,7 +120,7 @@ static __always_inline bool memory_is_poisoned_8(unsigned long addr)
> if (memory_is_poisoned_1(addr + 7))
> return true;
>
> - if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7))
> + if (likely(IS_ALIGNED(addr, 8)))
> return false;
Wouldn't IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE) be more appropriate?
But I'm not really sure what the original code is trying to do.
if ((addr + 7) & 7) >= 7)
can only evaluate true if ((addr + 7) & 7) equals 7, so the ">=" could
be "==".
I think. The code looks a bit weird. A code comment would help.
And how come memory_is_poisoned_16() does IS_ALIGNED(addr, 8)? Should
it be 16?
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Michal Marek <mmarek@suse.cz>,
"long.wanglong" <long.wanglong@huawei.com>,
Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>
Subject: Re: [PATCH] kasan: use IS_ALIGNED in memory_is_poisoned_8()
Date: Fri, 11 Sep 2015 15:47:30 -0700 [thread overview]
Message-ID: <20150911154730.3a2151a0b111fed01acdaaa1@linux-foundation.org> (raw)
In-Reply-To: <55F23635.1010109@huawei.com>
On Fri, 11 Sep 2015 10:02:29 +0800 Xishi Qiu <qiuxishi@huawei.com> wrote:
> Use IS_ALIGNED() to determine whether the shadow span two bytes.
> It generates less code and more readable.
>
Please cc Andrey Ryabinin on kasan patches.
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -120,7 +120,7 @@ static __always_inline bool memory_is_poisoned_8(unsigned long addr)
> if (memory_is_poisoned_1(addr + 7))
> return true;
>
> - if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7))
> + if (likely(IS_ALIGNED(addr, 8)))
> return false;
Wouldn't IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE) be more appropriate?
But I'm not really sure what the original code is trying to do.
if ((addr + 7) & 7) >= 7)
can only evaluate true if ((addr + 7) & 7) equals 7, so the ">=" could
be "==".
I think. The code looks a bit weird. A code comment would help.
And how come memory_is_poisoned_16() does IS_ALIGNED(addr, 8)? Should
it be 16?
--
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next prev parent reply other threads:[~2015-09-11 22:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-11 2:02 [PATCH] kasan: use IS_ALIGNED in memory_is_poisoned_8() Xishi Qiu
2015-09-11 2:02 ` Xishi Qiu
2015-09-11 22:47 ` Andrew Morton [this message]
2015-09-11 22:47 ` Andrew Morton
2015-09-14 1:17 ` Xishi Qiu
2015-09-14 1:17 ` Xishi Qiu
2015-09-14 13:19 ` Andrey Ryabinin
2015-09-14 13:19 ` Andrey Ryabinin
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