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SubjectRe: [PATCH 2/6] kexec jump: check code size in control page
On Thu, Aug 07, 2008 at 05:05:26PM +0800, Huang Ying wrote:
> Kexec/Kexec-jump requires code size in control page is less than
> PAGE_SIZE/2. This patch adds runtime checking for this.
>
> Signed-off-by: Huang Ying <ying.huang@intel.com>
>
> ---
> arch/x86/kernel/machine_kexec_32.c | 4 ++++
> arch/x86/kernel/relocate_kernel_32.S | 3 +++
> include/asm-x86/kexec.h | 1 +
> 3 files changed, 8 insertions(+)
>
> --- a/arch/x86/kernel/machine_kexec_32.c
> +++ b/arch/x86/kernel/machine_kexec_32.c
> @@ -92,6 +92,10 @@ int machine_kexec_prepare(struct kimage
> {
> 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);
> +

Hi Huang,

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.

Thanks
Vivek


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