linux-kernel - Re: [PATCH 2/3 -mm] kexec jump -v8 : add write support to oldmem device

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Date:	Fri, 21 Dec 2007 11:17:10 +0100
From:	Pavel Machek <pavel@....cz>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH 2/3 -mm] kexec jump -v8 : add write support to oldmem
	device

Hi!

> This patch adds writing support for /dev/oldmem. This can be used to
> 
> - Communicate between original kernel and kexeced kernel through write
>   to some pages in original kernel.
> 
> - Restore the memory contents of hibernated system in kexec based
>   hibernation.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> 
> --- a/arch/x86/kernel/crash_dump_32.c
> +++ b/arch/x86/kernel/crash_dump_32.c
> +ssize_t write_oldmem_page(unsigned long pfn, const char *buf,
> +			  size_t csize, unsigned long offset, int
> userbuf)

> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -348,6 +348,37 @@ static ssize_t read_oldmem(struct file *
>  	}
>  	return read;
>  }
> +
> +/*
> + * Write memory corresponding to the old kernel.
> + */
> +static ssize_t write_oldmem(struct file *file, const char __user *buf,
> +			    size_t count, loff_t *ppos)
> +{
...
> +		rc = write_oldmem_page(pfn, buf, csize, offset, 1);

I believe this is going to break compilation on non-32bit
machines. Or is crashdump only supported on i386?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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