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From: Mark Rutland <mark.rutland@arm.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Alexander Potapenko <glider@google.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/4] arm64/kasan: don't allocate extra shadow memory
Date: Thu, 1 Jun 2017 17:52:06 +0100	[thread overview]
Message-ID: <20170601165205.GA8191@leverpostej> (raw)
In-Reply-To: <CACT4Y+aCKDF95mK2-nuiV0+XineHha3y+6PCW0-EorOaY=TFng@mail.gmail.com>

On Thu, Jun 01, 2017 at 06:45:32PM +0200, Dmitry Vyukov wrote:
> On Thu, Jun 1, 2017 at 6:34 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Thu, Jun 01, 2017 at 07:23:37PM +0300, Andrey Ryabinin wrote:
> >> We used to read several bytes of the shadow memory in advance.
> >> Therefore additional shadow memory mapped to prevent crash if
> >> speculative load would happen near the end of the mapped shadow memory.
> >>
> >> Now we don't have such speculative loads, so we no longer need to map
> >> additional shadow memory.
> >
> > I see that patch 1 fixed up the Linux helpers for outline
> > instrumentation.
> >
> > Just to check, is it also true that the inline instrumentation never
> > performs unaligned accesses to the shadow memory?
> 
> Inline instrumentation generally accesses only a single byte.

Sorry to be a little pedantic, but does that mean we'll never access the
additional shadow, or does that mean it's very unlikely that we will?

I'm guessing/hoping it's the former!

Thanks,
Mark.

WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Alexander Potapenko <glider@google.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/4] arm64/kasan: don't allocate extra shadow memory
Date: Thu, 1 Jun 2017 17:52:06 +0100	[thread overview]
Message-ID: <20170601165205.GA8191@leverpostej> (raw)
In-Reply-To: <CACT4Y+aCKDF95mK2-nuiV0+XineHha3y+6PCW0-EorOaY=TFng@mail.gmail.com>

On Thu, Jun 01, 2017 at 06:45:32PM +0200, Dmitry Vyukov wrote:
> On Thu, Jun 1, 2017 at 6:34 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Thu, Jun 01, 2017 at 07:23:37PM +0300, Andrey Ryabinin wrote:
> >> We used to read several bytes of the shadow memory in advance.
> >> Therefore additional shadow memory mapped to prevent crash if
> >> speculative load would happen near the end of the mapped shadow memory.
> >>
> >> Now we don't have such speculative loads, so we no longer need to map
> >> additional shadow memory.
> >
> > I see that patch 1 fixed up the Linux helpers for outline
> > instrumentation.
> >
> > Just to check, is it also true that the inline instrumentation never
> > performs unaligned accesses to the shadow memory?
> 
> Inline instrumentation generally accesses only a single byte.

Sorry to be a little pedantic, but does that mean we'll never access the
additional shadow, or does that mean it's very unlikely that we will?

I'm guessing/hoping it's the former!

Thanks,
Mark.

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WARNING: multiple messages have this Message-ID (diff)
From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/4] arm64/kasan: don't allocate extra shadow memory
Date: Thu, 1 Jun 2017 17:52:06 +0100	[thread overview]
Message-ID: <20170601165205.GA8191@leverpostej> (raw)
In-Reply-To: <CACT4Y+aCKDF95mK2-nuiV0+XineHha3y+6PCW0-EorOaY=TFng@mail.gmail.com>

On Thu, Jun 01, 2017 at 06:45:32PM +0200, Dmitry Vyukov wrote:
> On Thu, Jun 1, 2017 at 6:34 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Thu, Jun 01, 2017 at 07:23:37PM +0300, Andrey Ryabinin wrote:
> >> We used to read several bytes of the shadow memory in advance.
> >> Therefore additional shadow memory mapped to prevent crash if
> >> speculative load would happen near the end of the mapped shadow memory.
> >>
> >> Now we don't have such speculative loads, so we no longer need to map
> >> additional shadow memory.
> >
> > I see that patch 1 fixed up the Linux helpers for outline
> > instrumentation.
> >
> > Just to check, is it also true that the inline instrumentation never
> > performs unaligned accesses to the shadow memory?
> 
> Inline instrumentation generally accesses only a single byte.

Sorry to be a little pedantic, but does that mean we'll never access the
additional shadow, or does that mean it's very unlikely that we will?

I'm guessing/hoping it's the former!

Thanks,
Mark.

  reply	other threads:[~2017-06-01 16:53 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-01 16:23 [PATCH 1/4] mm/kasan: get rid of speculative shadow checks Andrey Ryabinin
2017-06-01 16:23 ` Andrey Ryabinin
2017-06-01 16:23 ` [PATCH 2/4] x86/kasan: don't allocate extra shadow memory Andrey Ryabinin
2017-06-01 16:23   ` Andrey Ryabinin
2017-06-01 16:23 ` [PATCH 3/4] arm64/kasan: " Andrey Ryabinin
2017-06-01 16:23   ` Andrey Ryabinin
2017-06-01 16:23   ` Andrey Ryabinin
2017-06-01 16:34   ` Mark Rutland
2017-06-01 16:34     ` Mark Rutland
2017-06-01 16:34     ` Mark Rutland
2017-06-01 16:45     ` Dmitry Vyukov
2017-06-01 16:45       ` Dmitry Vyukov
2017-06-01 16:45       ` Dmitry Vyukov
2017-06-01 16:52       ` Mark Rutland [this message]
2017-06-01 16:52         ` Mark Rutland
2017-06-01 16:52         ` Mark Rutland
2017-06-01 16:59         ` Andrey Ryabinin
2017-06-01 16:59           ` Andrey Ryabinin
2017-06-01 16:59           ` Andrey Ryabinin
2017-06-01 17:00           ` Andrey Ryabinin
2017-06-01 17:00             ` Andrey Ryabinin
2017-06-01 17:00             ` Andrey Ryabinin
2017-06-01 17:05             ` Dmitry Vyukov
2017-06-01 17:05               ` Dmitry Vyukov
2017-06-01 17:05               ` Dmitry Vyukov
2017-06-01 17:38               ` Dmitry Vyukov
2017-06-01 17:38                 ` Dmitry Vyukov
2017-06-01 17:38                 ` Dmitry Vyukov
2017-06-01 16:23 ` [PATCH 4/4] mm/kasan: Add support for memory hotplug Andrey Ryabinin
2017-06-01 16:23   ` Andrey Ryabinin
2017-06-01 17:45 ` [PATCH 1/4] mm/kasan: get rid of speculative shadow checks Dmitry Vyukov
2017-06-01 17:45   ` Dmitry Vyukov

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