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From:   Daniel Colascione <dancol@google.com>
Date:   Sat, 19 Jan 2019 12:43:35 -0500
Message-ID: <CAKOZuet+7a4jdox6rebMN=kJtDn5RUYzvNjFh+Pzn2UkuP0Y8Q@mail.gmail.com>
Subject: Re: [RFC] Provide in-kernel headers for making it easy to extend the kernel
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>, ast@kernel.org,
        atishp04@gmail.com, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Jan Kara <jack@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        karim.yaghmour@opersys.com, Kees Cook <keescook@chromium.org>,
        kernel-team@android.com,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Manoj Rao <linux@manojrajarao.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Randy Dunlap <rdunlap@infradead.org>, rostedt@goodmis.org,
        Thomas Gleixner <tglx@linutronix.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        yhs@fb.com
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On Sat, Jan 19, 2019 at 11:27 AM Joel Fernandes <joel@joelfernandes.org> wrote:
>
> On Sat, Jan 19, 2019 at 09:25:32AM +0100, Greg KH wrote:
> > On Fri, Jan 18, 2019 at 05:55:43PM -0500, Joel Fernandes wrote:
> > > --- /dev/null
> > > +++ b/kernel/kheaders.c

Thanks a ton for this work. It'll make it much easier to do cool
things with BPF. One question: I can imagine wanting to probe
structures that are defined, not in headers, but in random
implementation files. Would it be possible to optionally include *all*
kernel source files? If not, what about a hash, so we could at least
do precise correlation between a candidate local tree and what's
actually on device?

BTW, I'm not sure that the magic constants you've defined are long
enough.  I'd feel more comfortable with two UUIDs (16 bytes each).

I'd also strongly consider LZMA compression: xz -9 on the kernel
headers (with comments) brings the size down to 5MB, compared to the
7MB I get for gzip -9. Considering that this feature is optional, I
think it's okay to introduce a dependency on widespread modern
compression tools. (For comparison, bzip2 -9 gets us 6MB.)