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

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Date:   Thu, 15 Dec 2016 20:09:27 +0200
From:   Nikolay Borisov <n.borisov.lkml@...il.com>
To:     linux-kbuild@...r.kernel.org
Cc:     LKML <linux-kernel@...r.kernel.org>, yann.morin.1998@...e.fr,
        mmarek@...e.com
Subject: default 0 if KASAN expression not working in kbuild

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.

Regards,
Nikolay