Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20190410224213.20651-1-okaya@kernel.org> <CAGXu5jKzBGRr7LjFVdpvHhSFV7C7kuj-6VphhtLsMEoetr_R7g@mail.gmail.com>
 <135E84E9-F068-44CB-B4F6-A5AC2F4CDE3D@joshtriplett.org> <CAGXu5jLc_Z=TiNsMd40GN8-0D117RVbdD7Hy4MzjPQNbFf=bcg@mail.gmail.com>
 <FF2E07CA-99D7-4F9C-B281-425897535C84@joshtriplett.org> <e901a9cc-f335-fb31-535c-97dce2ca8f5b@kernel.org>
 <20190411221645.GA8692@localhost>
In-Reply-To: <20190411221645.GA8692@localhost>
From:   Kees Cook <keescook@chromium.org>
Date:   Thu, 11 Apr 2019 15:21:09 -0700
Message-ID: <CAGXu5jKa4dUuCxc1kPdRGH5qrXeH0y09hnScb41-SQDo_amv8Q@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>, Kees Cook <keescook@chromium.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>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Apr 11, 2019 at 3:16 PM Josh Triplett <josh@joshtriplett.org> wrote:
>
> On Wed, Apr 10, 2019 at 11:13:52PM -0400, Sinan Kaya wrote:
> > On 4/10/2019 11:02 PM, Josh Triplett wrote:
> > > Then let's fix*that*, and get checkpatch to help enforce it in the future. EXPERT doesn't affect code generation, and neither should this.
> >
> > I think we have to do both. We need to go after the users as well as
> > solve the immediate problem per this patch.
> >
> > As Mathieu identified, CONFIG_DEBUG_KERNEL is being used all over the
> > place and getting subsystem owners to remove let alone add a check
> > to checkpatch is just going to take time.
> >
> > Please let us know if you are OK with this plan.
>
> I'm not OK with this plan. Turning on EXPERT should make the options
> under DEBUG_KERNEL visible; it's a bug that DEBUG_KERNEL affects code
> generation as well.
>
> Proposed alternative plan: let's add a new symbol, something like
> DEBUG_MISC ("Miscellaneous debug code that should be under a more
> specific debug option but isn't"), make it depend on DEBUG_KERNEL and be
> "default DEBUG_KERNEL" but allow itself to be turned off, and then
> mechanically change the small handful of "#ifdef CONFIG_DEBUG_KERNEL" to
> "#ifdef CONFIG_DEBUG_MISC".
>
> Does that sound like an appropriately rapid solution for this bug?

Sure, that sounds fine to me. Sinan can you take care of that for v4?

-- 
Kees Cook