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

[Pavel Machek]

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 at intel.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
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