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Subject: Re: [PATCH] kasan: turn off asan-stack for clang-8 and earlier
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Andrey Konovalov <andreyknvl@google.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Michal Marek <michal.lkml@markovi.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Mark Brown <broonie@kernel.org>, Qian Cai <cai@lca.pw>,
        Alexander Potapenko <glider@google.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Christoph Lameter <cl@linux.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>
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From:   Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <8e29f564-88e1-90b0-948c-d2fb52db29b9@virtuozzo.com>
Date:   Thu, 21 Feb 2019 19:14:30 +0300
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On 2/21/19 6:19 PM, Arnd Bergmann wrote:
> On Thu, Feb 21, 2019 at 11:06 AM Andrey Ryabinin
> <aryabinin@virtuozzo.com> wrote:
>> On 2/20/19 8:35 PM, Arnd Bergmann wrote:
>>> On Wed, Feb 20, 2019 at 6:00 PM Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>>>> On 2/20/19 5:51 PM, Arnd Bergmann wrote:
> 
>>> Maybe bringing it back would be a compromise? That way it's hidden from
>>> all the build testing bots (because of the !CONFIG_COMPILE_TEST dependency),
>>> but anyone who really wants it can still have the option, and set
>>> CONFIG_FRAME_WARN
>>> to whichever value they like.
>>>
>>
>>
>> I think there is much simpler solution:
>>
>> ---
>>  lib/Kconfig.kasan | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
>> index 219cddc913ac..6cd035f06cee 100644
>> --- a/lib/Kconfig.kasan
>> +++ b/lib/Kconfig.kasan
>> @@ -105,6 +105,8 @@ endchoice
>>
>>  config KASAN_STACK
>>         int
>> +       range 0 1
>> +       prompt "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && (CLANG_VERSION < 90000)
>>         default 0 if CC_IS_CLANG && (CLANG_VERSION < 90000)
>>         default 1
>>         help
>> --
>>
>>
>> AFAIK, randconfig is not able to randomize int config options, so it will be disabled for build robots,
>> but users still will be able to enable it.
> 
> Right, this will work, but I find it a bit awkward to require users to
> enter 0 or 1.
> 
> My assumption is that build bots turn on CONFIG_COMPILE_TEST, so
> having a bool option that depends on COMPILE_TEST would be more
> conventional. We can debate whether it should also depend on
> CONFIG_EXPERT or not. Something like
> 
> config KASAN_STACK
>          bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG
> && !COMPILE_TEST
>          default CC_IS_GCC || (CLANG_VERSION >= 90000)
> 
> And then a simpler Makefile logic (could also be done in Kconfig) to turn
> that bool symbol into an integer argument for asan-stack=
> 

Sounds good.