linux-kernel - [Fwd: Fwd: Re: Why is dynamic debug disabled for staging drivers ?]

Open Source and information security mailing list archives

Date:	Wed, 06 Apr 2011 08:34:35 -0700
From:	Joe Perches <joe@...ches.com>
To:	Jason Baron <jbaron@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Roland Vossen <rvossen@...adcom.com>,
	devel <devel@...uxdriverproject.org>, gregkh@...e.de
Subject: [Fwd: Fwd: Re: Why is dynamic debug disabled for staging drivers ?]

Adding Jason and LKML. to cc's...

-------- Forwarded Message --------
From: Roland Vossen <rvossen@...adcom.com>
To: rusty@...tcorp.com.au
Cc: devel@...uxdriverproject.org <devel@...uxdriverproject.org>,
gregkh@...e.de <gregkh@...e.de>
Subject: Fwd: Re: Why is dynamic debug disabled for staging drivers ?
Date: Wed, 6 Apr 2011 17:09:04 +0200

Hello Rusty,

I would like to make a change to module.c and noticed with 'git blame' 
that you were the last person who touched these specific lines in module.c:

http://lxr.linux.no/#linux+v2.6.38/kernel/module.c#L2792

===== Corresponding commit for your reference:

commit 811d66a0e1e99902d365497eec7884113a2665bd
Author: Rusty Russell <rusty@...tcorp.com.au>
Date:   Thu Aug 5 12:59:12 2010 -0600

module: group post-relocation functions into post_relocation()

This simply hoists more code out of load_module; we also put the
identification of the extable and dynamic debug table in with the
others in find_module_sections().

We move the taint check to the actual add/remove of the dynamic debug
info: this is certain (find_module_sections is too early).

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Cc: Yehuda Sadeh <yehuda@...newdream.net>

==============

Can you tell me if the following proposed code change in module.c is ok 
with you:

	/* This has to be done once we're sure module name is unique. */
	if (!mod->taints || mod->taints == (1U << TAINT_CRAP))
		dynamic_debug_setup(info.debug, info.num_debug);

Thanks, Roland.

-------- Original Message --------
Subject: Re: Why is dynamic debug disabled for staging drivers ?
Date: Wed, 6 Apr 2011 07:13:29 -0700
From: Greg KH <greg@...ah.com>
To: Roland Vossen <rvossen@...adcom.com>
CC: devel@...uxdriverproject.org <devel@...uxdriverproject.org>

On Wed, Apr 06, 2011 at 03:54:37PM +0200, Roland Vossen wrote:
> Hi,
>
> I want to replace the proprietary logging mechanism in brcm80211
> with a Linux mechanism. 'Dynamic debug' seemed to be a good fit.
> But, to my disappointment, I discovered that dynamic debugging is
> not supported for drivers from the staging dir:
>
> - staging drivers are marked tainted (ref:
> http://lxr.linux.no/#linux+v2.6.38/kernel/module.c#L2417)
>
> - subsequently tainted drivers don't get dynamic debug goodies (ref:
> http://lxr.linux.no/#linux+v2.6.38/kernel/module.c#L2792)
>
> I wonder if this is intentional behavior. Does anybody know ?

Ah, no it isn't.  I didn't realize that tainted modules didn't get
dynamic debug stuff, that's not nice.  I'd be glad to take a fix that
allows drivers tainted with the TAINT_CRAP flag to be able to use
dynamic debug.

In looking at that check, it probably can be fixed to just make sure
that the module name is unique (i.e. only a specific taint flag check)
which is the real goal of that check in module.c.

thanks,

greg k-h

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