[boot-wrapper PATCH v2 7/9] pointer auth: Document CPU feature bit mask

[Mark Rutland]

On Wed, Dec 22, 2021 at 06:16:05PM +0000, Andre Przywara wrote:
> When checking for the pointer authentication feature, we actually look
> for *four* different CPUID feature sets.
> Add a comment to make it more obvious that the 0xff is not a typo.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>

Thanks; applied.

Mark.

> ---
>  arch/aarch64/boot.S | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
> index bfbb6ec..27ba449 100644
> --- a/arch/aarch64/boot.S
> +++ b/arch/aarch64/boot.S
> @@ -38,7 +38,8 @@ ASM_FUNC(_start)
>  
>  	/* Enable pointer authentication if present */
>  	mrs	x1, id_aa64isar1_el1
> -	ldr	x2, =(((0xff) << 24) | (0xff << 4))
> +	/* We check for APA+API and GPA+GPI */
> +	ldr	x2, =((0xff << 24) | (0xff << 4))
>  	and	x1, x1, x2
>  	cbz	x1, 1f
>  
> -- 
> 2.25.1
>