linux-kernel - Re: [RFC] Provide in-kernel headers for making it easy to extend the kernel

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Message-ID: <20190124141820.GA75378@google.com>
Date:   Thu, 24 Jan 2019 09:18:20 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Daniel Colascione <dancol@...gle.com>
Cc:     Karim Yaghmour <karim.yaghmour@...rsys.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Christoph Hellwig <hch@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, ast@...nel.org,
        atish patra <atishp04@...il.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Jan Kara <jack@...e.cz>, Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>, kernel-team@...roid.com,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Manoj Rao <linux@...ojrajarao.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>, rostedt@...dmis.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        yhs@...com
Subject: Re: [RFC] Provide in-kernel headers for making it easy to extend the
 kernel

On Wed, Jan 23, 2019 at 09:32:16PM -0500, Joel Fernandes wrote:
> On Wed, Jan 23, 2019 at 02:37:47PM -0800, Daniel Colascione wrote:
> > On Wed, Jan 23, 2019 at 1:29 PM Karim Yaghmour
> > <karim.yaghmour@...rsys.com> wrote:
> [...]
> > > Personally I advocated a more aggressive approach with Joel in private:
> > > just put the darn headers straight into the kernel image, it's the
> > > *only* artifact we're sure will follow the Android device whatever
> > > happens to it (like built-in ftrace).
> > 
> > I was thinking along similar lines. Ordinarily, we make loadable
> > kernel modules. What we kind of want here is a non-loadable kernel
> > module --- or a non-loadable section in the kernel image proper. I'm
> > not familiar with early-stage kernel loader operation: I know it's
> > possible to crease discardable sections in the kernel image, but can
> > we create sections that are never slurped into memory in the first
> > place? If not, maybe loading and immediately discarding the header
> > section is good enough.
> 
> I am happy to see if I can shrink it down further. Especially using xz and
> stripping all comments period. I am optimistic this can be brought down
> further to a point where it would make sense to everyone to build it into the
> kernel. Lets see.
> 
> Last time I stripped comments, it went down by ~40%. What I haven't tried is
> doing this *with* xz compression. I am also open to brainstorming what else
> can be stripped.

Removing comments (/* */) with xz compression brings it down to 3.3MB.

thanks,

 - Joel