linux-kernel - Re: [PATCH v5 1/3] Provide in-kernel headers to make extending kernel easier

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Message-ID: <79b6bdbc-890a-5a51-7fa1-aec57889046a@opersys.com>
Date:   Mon, 8 Apr 2019 16:52:18 -0400
From:   Karim Yaghmour <karim.yaghmour@...rsys.com>
To:     Olof Johansson <olof@...om.net>, joel@...lfernandes.org
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        qais.yousef@....com, dietmar.eggemann@....com,
        linux@...ojrajarao.com, Andrew Morton <akpm@...ux-foundation.org>,
        ast@...nel.org, atishp04@...il.com, dancol@...gle.com,
        Dan Williams <dan.j.williams@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-trace-devel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        mhiramat@...nel.org, Randy Dunlap <rdunlap@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shuah Khan <shuah@...nel.org>, yhs@...com
Subject: Re: [PATCH v5 1/3] Provide in-kernel headers to make extending kernel
 easier


Hi Olof,

On 4/8/19 12:29 PM, Olof Johansson wrote:
> Sorry to be late at the party with this kind of feedback, but I find
> the whole ".tar.gz in procfs" to be an awkward solution, especially if
> there's expected to be userspace tooling that depends on this
> long-term.
> 
> Wouldn't it be more convenient to provide it in a standardized format
> such that you won't have to take an additional step, and always have
> it in a known location?
> 
> Something like:
> 
>   - Pseudo-filesystem, that can just be mounted under
> /sys/kernel/headers or something (similar to debugfs or
> /proc/device-tree).
>   - Exporting something like a squashfs image instead, allowing
> loopback mounting of it (or by providing a pseudo-/dev entry for it),
> again allowing direct export of the contents and avoiding the
> extracted directory from being out of sync with currently running
> kernel.
> 
> Having to copy and extract the tarball is the most awkward step, IMHO.
> I also find the waste of kernel memory for it to be an issue, but
> given that it can be built as a module I guess that's the obvious
> solution for those who care about memory consumption.

One of the things I pointed out earlier in the thread is that 
/proc/config.gz has already set a precedent as to the interface for this 
sort of artifact. It's a plain compressed file and it's directly 
accessible from toplevel /proc. From a consistency perspective there's 
an idiomatic angle to some sort of "/proc/kheaders.gz".

In some offline discussions I was also told that squashfs (I'm no expert 
of it) required special user-space tools and had some security issues.

Cheers,

-- 
Karim Yaghmour
CEO - Opersys inc. / www.opersys.com
http://twitter.com/karimyaghmour