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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 10 Apr 2019 15:58:55 -0700
Message-ID: <CAGXu5jKzBGRr7LjFVdpvHhSFV7C7kuj-6VphhtLsMEoetr_R7g@mail.gmail.com>
Subject: Re: [PATCH v2] init: Do not select DEBUG_KERNEL by default
To:     Sinan Kaya <okaya@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Adrian Reber <adrian@lisas.de>,
        Richard Guy Briggs <rgb@redhat.com>,
        Petr Mladek <pmladek@suse.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Mikulas Patocka <mpatocka@redhat.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Changbin Du <changbin.du@intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Sam Ravnborg <sam@ravnborg.org>, Ingo Molnar <mingo@kernel.org>
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On Wed, Apr 10, 2019 at 3:42 PM Sinan Kaya <okaya@kernel.org> wrote:
>
> We can't seem to have a kernel with CONFIG_EXPERT set but
> CONFIG_DEBUG_KERNEL unset these days.
>
> While some of the features under the CONFIG_EXPERT require
> CONFIG_DEBUG_KERNEL, it doesn't apply for all features.
>
> It looks like CONFIG_KALLSYMS_ALL is the only feature that
> requires CONFIG_DEBUG_KERNEL.
>
> Select CONFIG_EXPERT when CONFIG_DEBUG is chosen but you can

Typo: CONFIG_DEBUG_KERNEL

> still choose CONFIG_EXPERT without CONFIG_DEBUG.

same.

>
> Signed-off-by: Sinan Kaya <okaya@kernel.org>

But with those fixed, looks good to me. Adding Josh (and others) to CC
since he originally added the linkage to EXPERT in commit
f505c553dbe2.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  init/Kconfig      | 2 --
>  lib/Kconfig.debug | 1 +
>  2 files changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 4592bf7997c0..37e10a8391a3 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1206,8 +1206,6 @@ config BPF
>
>  menuconfig EXPERT
>         bool "Configure standard kernel features (expert users)"
> -       # Unhide debug options, to make the on-by-default options visible
> -       select DEBUG_KERNEL
>         help
>           This option allows certain base kernel options and settings
>            to be disabled or tweaked. This is for specialized
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 0d9e81779e37..9fbf3499ec8d 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -434,6 +434,7 @@ config MAGIC_SYSRQ_SERIAL
>
>  config DEBUG_KERNEL
>         bool "Kernel debugging"
> +       default EXPERT
>         help
>           Say Y here if you are developing drivers or trying to debug and
>           identify kernel problems.
> --
> 2.21.0
>


-- 
Kees Cook