linux-kernel - Re: module: add debugging alias parsing support

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Message-ID: <20171130183947.GI729@wotan.suse.de>
Date:   Thu, 30 Nov 2017 19:39:47 +0100
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Jessica Yu <jeyu@...nel.org>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>, jeyu@...hat.com,
        rusty@...tcorp.com.au, keescook@...omium.org, tixxdz@...il.com,
        mbenes@...e.cz, atomlin@...hat.com, pmladek@...e.com,
        hare@...e.com, james.l.morris@...cle.com, ebiederm@...ssion.com,
        davem@...emloft.net, akpm@...ux-foundation.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: module: add debugging alias parsing support

On Thu, Nov 30, 2017 at 02:17:11PM +0100, Jessica Yu wrote:
> Just some quick questions - are there any plans to use these in-kernel
> module aliases anywhere else? Or are you using them just for debugging?

As-is for now just debugging, but this could also more easily enable folks to
prototype further evaluation of its uses. IMHO just having this at least posted
online should suffice the later aspect of enabling folks to prototype.

You're right that one can find aliases in userspace. One of the benefits
of having this dump things on the kernel log is just that you can easily
get the aliases printed out for all modules actually loaded for your system
without much effort. I did find this useful when debugging and found it much
more convenient than scraping modules one by one by hand in userspace.

I had this implemented since 2016, and I had some ideas to use them in a
functional way, however I first had to knock out a series of of fixes for
kernel/kmod.c and setting up a baseline test infrastructure for kmod
(tools/testing/selftests/kmod/ and lib/test_kmod.c) as such I hadn't had time
to yet come around and finish benchmarking the alias enhancement ideas I had
started evaluating.

As such having aliases in-kernel currently are only useful for debugging and
prototyping.

  Luis