linux-kernel - Re: [PATCH 01/26] compiler: introduce noinline_for

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Date:   Fri, 3 Mar 2017 15:51:41 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Networking <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        kernel-build-reports@...ts.linaro.org,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 01/26] compiler: introduce noinline_for_kasan annotation

On Fri, Mar 3, 2017 at 3:33 PM, Alexander Potapenko <glider@...gle.com> wrote:
> On Fri, Mar 3, 2017 at 3:30 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Fri, Mar 3, 2017 at 2:55 PM, Alexander Potapenko <glider@...gle.com> wrote:
>>
>> Would KMSAN also force local variables to be non-overlapping the way that
>> asan-stack=1 and -fsanitize-address-use-after-scope do? As I understood it,
>> KMSAN would add extra code for maintaining the uninit bits, but in an example
>> like this
> The thing is that KMSAN (and other tools that insert heavyweight
> instrumentation) may cause heavy register spilling which will also
> blow up the stack frames.

In that case, I would expect a mostly distinct set of functions to have large
stack frames with KMSAN, compared to the ones that need
noinline_for_kasan. In most cases I patched, the called inline function is
actually trivial, but invoked many times from the same caller.

     Arnd