linux-kernel - RE: [RFC] export module parameters even the permission is zero

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Message-ID: <35FD53F367049845BC99AC72306C23D1044A02027DE0@CNBJMBX05.corpusers.net>
Date:	Thu, 22 Jan 2015 10:07:49 +0800
From:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
To:	'Rusty Russell' <rusty@...tcorp.com.au>,
	"'akpm@...ux-foundation.org'" <akpm@...ux-foundation.org>,
	"'jani.nikula@...el.com'" <jani.nikula@...el.com>,
	"'hch@...radead.org'" <hch@...radead.org>,
	"'hare@...e.de'" <hare@...e.de>,
	"'keescook@...omium.org'" <keescook@...omium.org>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC] export module parameters even the permission is zero

> -----Original Message-----
> From: Rusty Russell [mailto:rusty@...tcorp.com.au]
> Sent: Tuesday, January 20, 2015 2:33 PM
> To: Wang, Yalin; 'akpm@...ux-foundation.org'; 'jani.nikula@...el.com';
> 'hch@...radead.org'; 'hare@...e.de'; 'keescook@...omium.org'; 'linux-
> kernel@...r.kernel.org'
> Subject: Re: [RFC] export module parameters even the permission is zero
> 
> "Wang, Yalin" <Yalin.Wang@...ymobile.com> writes:
> > This patch make sure to export module parameters even the permission
> > is zero, this is useful for some platforms like Android, the init
> > process can change the parameter mode/owner by chmod/chown during
> > bootup
> >
> > Signed-off-by: Yalin Wang <yalin.wang@...ymobile.com>
> 
> Hi!
> 
>         Unfortunately, this won't work.  Various parts of the code assume
> that 0 permissions means "cannot be changed or read", so this change would
> introduce many bugs (eg. the parameter could be __initdata).
> 
> Since these are owned by root at boot, changing mode and owner should still
> work.  However, you can't make a read-only field writable and expect it to
> work.
> 
Oh, I see,
This means kernel cmdline can change this module_parameter ignored permission,

Thanks for your comments.
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