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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 10 Apr 2019 16:24:18 -0700
Message-ID: <CAGXu5jLc_Z=TiNsMd40GN8-0D117RVbdD7Hy4MzjPQNbFf=bcg@mail.gmail.com>
Subject: Re: [PATCH v2] init: Do not select DEBUG_KERNEL by default
To:     Josh Triplett <josh@joshtriplett.org>
Cc:     Sinan Kaya <okaya@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Andrew Morton <akpm@linux-foundation.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>,
        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 4:22 PM Josh Triplett <josh@joshtriplett.org> wrote:
>
> On April 10, 2019 3:58:55 PM PDT, Kees Cook <keescook@chromium.org> wrote:
> >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.
>
> CONFIG_DEBUG_KERNEL shouldn't affect code generation in any way; it should only make more options appear in kconfig. I originally added this to ensure that features you might want to *disable* aren't hidden, as part of the tinification effort.
>
> What specific problem does having CONFIG_DEBUG_KERNEL enabled cause for you? I'd still prefer to have a single switch for "don't hide things I might want to disable", rather than several.

See earlier in the thread: code generation depends on
CONFIG_DEBUG_KERNEL now unfortunately.

-- 
Kees Cook