Re: [PATCH v7u1 22/31] x86, boot: add fields to support load bzImageand ramdisk above 4G

[Borislav Petkov]

On Mon, Jan 14, 2013 at 10:57:08AM -0800, Yinghai Lu wrote:
> please check if following is enough?
> 
> +       /*
> +        * kernel have sentinel to set as 0xff in setup link scripts,
> +        * so if bootloader just copy whole page from kernel image to
> +        * get setup_header instead of clearing boot_param buffer and
> +        * copying setup_header only, will leave sentinel as 0xff.
> +        * With that, we can tell some fields in boot_param have
> +        * invalid values, and we need to zero them in kernel.
> +        */
> +       __u8  sentinel;                                 /* 0x1ef */

"The sentinel variable is set by the linker script to 0xff. If a
bootloader doesn't know about this variable and just copies the
setup_header portion and doesn't clear the boot_params buffer as it is
supposed to, it will leave the sentinel to its initial value of 0xff.

This tells the kernel that some fields in boot_params have invalid
values and we have to zero them out in the kernel."

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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