[PATCHv6 4/8] arm64: Move some head.text functions to executable section

[mark.rutland@arm.com (Mark Rutland)]

Hi Laura,

On Fri, Nov 21, 2014 at 09:50:41PM +0000, Laura Abbott wrote:
> The head.text section is intended to be run at early bootup
> before any of the regular kernel mappings have been setup.
> Parts of head.text may be freed back into the buddy allocator
> due to TEXT_OFFSET so for security requirements this memory
> must not be executable. The suspend/resume/hotplug code path
> requires some of these head.S functions to run however which
> means they need to be executable. Support these conflicting
> requirements by moving the few head.text functions that need
> to be executable to the text section which has the appropriate
> page table permissions.
> 
> Tested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>

Other than a minor nit below this looks good to me, and I'm not seeing
any issues with boot, hotplug, or idle, so:

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>

Thanks for putting this together!

> ---
> v6: Dropped the latehead.text bit and just moved everything to the regular
> text section
> ---
>  arch/arm64/kernel/head.S | 407 ++++++++++++++++++++++++-----------------------
>  1 file changed, 210 insertions(+), 197 deletions(-)
> 
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 10f5cc0..4b63d7a 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -238,7 +238,13 @@ ENTRY(stext)
>         mov     x0, x22
>         bl      lookup_processor_type
>         mov     x23, x0                         // x23=current cpu_table
> -       cbz     x23, __error_p                  // invalid processor (x23=0)?
> +       /*
> +        *      __error_p may end up out of range for cbz if text areas
> +        *      are aligned up to section sizes
> +        */

Nit: We don't need to align the comment text (we don't for the comment a
few lines later, or any others in this file). It would be nice to keep
that consistent.

Thanks,
Mark.