linux-kernel - Re: [PATCH 0/3] Implement /proc/built-in file similar to /proc/modules

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Message-ID: <5415D10E.90809@yandex.ru>
Date:	Sun, 14 Sep 2014 21:31:58 +0400
From:	Kirill Tkhai <tkhai@...dex.ru>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	mmarek@...e.cz, arnd@...db.de, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, oleg@...hat.com,
	grant.likely@...retlab.ca, ebiederm@...ssion.com,
	akpm@...ux-foundation.org, ktkhai@...allels.com, sam@...nborg.org
Subject: Re: [PATCH 0/3] Implement /proc/built-in file similar to /proc/modules

On 14.09.2014 19:38, Greg KH wrote:
> On Sun, Sep 14, 2014 at 02:18:13PM +0400, Kirill Tkhai wrote:
>> This series implements a possibility to show the list of built-in drivers
>> to userspace. The names of drivers will be the same as when they are modules.
> 
> Have you looked at /sys/modules/ ?  Doesn't that show what you want
> here?

There are only the drivers in "/sys/module" which have parameters.
Drivers without parameters do not appear there.

>> So, if your system has "loop" driver then it appears either in /proc/modules
>> or in /proc/built-in and userspace will be able to know about this.
>>
>> Now this is impossible. The only way to get kernel configuration is
>> /proc/config.gz, but CONFIG_* names can change from time to time. Module
>> names are more or less standardized.
> 
> Module names aren't "standardized", we change them at times when needed,
> just like CONFIG_ names.
> 
> What is your end goal here?  As you say, config.gz is the real kernel
> configuration, just having a list of modules built in isn't going to
> help much in getting a working kernel config without it.

It looks like userspace applications oriented on modules names rather
than on CONFIG_XXX parameters. /proc/config.gz is optional and userspace
applications can't base on it.

For example, when I compile "loop" module built-in and "loop" is in
/etc/modules, init script warns about this module is not present and
can't be autoloaded. The script does not store CONFIG_XXX <-> module_xxx
conformity. And nobody stores it.

When iptables wants extra functionality, it requests a module. Etc.

Nobody is oriented on CONFIG_XXX parameters. It would be simple for
userspace to add a support of /proc/built-in analysing. It's very
similar to /proc/modules.
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