linux-kernel - Re: default 0 if KASAN expression not working in kbuild

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Message-ID: <a7a212c3-02f6-ce32-07fc-f073b2080ff8@gmail.com>
Date:   Fri, 16 Dec 2016 09:50:35 +0200
From:   Nikolay Borisov <n.borisov.lkml@...il.com>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kbuild@...r.kernel.org
Cc:     LKML <linux-kernel@...r.kernel.org>, yann.morin.1998@...e.fr,
        mmarek@...e.com
Subject: Re: default 0 if KASAN expression not working in kbuild



On 15.12.2016 23:32, Randy Dunlap wrote:
> On 12/15/16 10:09, Nikolay Borisov wrote:
>> Hello,
>>
>> I was doing some kasan-related debugging and when I enabled it I started
>> getting warnings for large stackframes. So CONFIG_FRAME_WARN has :
>>
>> int "Warn for stack frames larger than (needs gcc 4.4)"
>>     range 0 8192
>>     default 0 if KASAN
>>     default 2048 if GCC_PLUGIN_LATENT_ENTROPY
>>     default 1024 if !64BIT
>>     default 2048 if 64BIT
>>
>> This means that frame_warns should effectively be disabled when kasan is
>> enabled. However in my case this is not the situation.
>> http://sprunge.us/FiGf here is the config file. It does have
>> CONFIG_KASAN=y and CONFIG_FRAME_WARN=1024 . And even this is erroneous
>> since it's a 64bit kernel, so it should be 2k. I haven't manually set
>> the limit to 1k either.
> 
> Yeah, it set FRAME_WARN=1024 for me also.
> 
> It seems to be dependent on order of kconfig symbols in
> lib/Kconfig.debug.
> 
> If I move the line:
>   source "lib/Kconfig.kasan"
> to just after this line:
>   menu "Compile-time checks and compiler options"
> it seems to work for me.
> 
> Can you test the patch below?

This patch has another problem that if I move the source line then I no
longer get the kasan option in Memory Debugging section, furthermore the
frame_warn wasn't changed either.


>