linux-kernel - Re: [PATCH 2/6] kexec jump: check code size in control page

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Message-ID: <20080807203130.GA10331@ucw.cz>
Date:	Thu, 7 Aug 2008 22:31:30 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Huang Ying <ying.huang@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH 2/6] kexec jump: check code size in control page

Hi!

> > PAGE_SIZE/2. This patch adds runtime checking for this.
> > 
> > Signed-off-by: Huang Ying <ying.huang@...el.com>
...

> >  {
> >  	if (nx_enabled)
> >  		set_pages_x(image->control_code_page, 1);
> > +
> > +	BUG_ON((unsigned long)kexec_control_page_code_end - \
> > +	       (unsigned long)relocate_kernel >= PAGE_SIZE/2);
> > +
> 

> Run time check is better than nothing but I think in this case it would
> be better if we can catch it at compile time. 
> 
> One of the methods will be to write a small program of your own and
> put in script/ and at build time check for the size and flag error. May
> be there are other better ways to do this.

BUILD_BUG_ON()?

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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